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  • What do you need to know to be a world-class master software developer? [closed]

    - by glitch
    I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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  • Oracle/Sun ?????? - SPARC SuperCluster T4-4

    - by user12798668
    SPARC SuperCluster T4-4 ?????????? SPARC SuperCluster ? 2010?12?????·???????????????????? 2011 ? 9 ?? SPARC T4 ???????????? SPARC SuperCluster T4-4 ????????????????SPARC SuperCluster ??????????·??????????????????????????? SPARC T4 CPU ? 4 ????? SPARC T4-4 ??????????????????????·????????????????????? Exadata ????????????? Oracle Exadata Storage Server ????????????? Java ????????? Exalogic ????????????? Exalogic Software ???????????????????????? Solaris 10 ??? 11 ??????????????????????? SPARC SuperCluster ? ???????????????????? ???????????????????????SPARC SuperCluster ? Oracle/Sun ???????????????????????????????????? SPARC SuperCluster ??????????? 2(Half Rack ?) or 4(Full Rack ?) x SPARC T4-4 ???? 3 (Half Rack ?) or 6 (Full Rack ?) x Exadata Storage Server X2-2 1 x ZFS Storage Appliance 7320 ?????? 3 x Sun DataCenter InfiniBand Switch 36 1 x Ethernet Management Switch 42U Rack (2 x PDU) SPARC SuperCluster ????????????? OS: Oracle Solaris 11 ??? 10 ???: Oracle VM Server for SPARC ??? Oracle Solaris Zones ??: Oracle Enterprise Manager Ops Center ??? Grid Control ???????: Oracle Solaris Cluster ??? Oracle Clusterware ??????: Oracle ?????? 11g R2 (11.2.0.3) ???????????? ??????: Exalogic Software ???? Oracle WebLogic Server, Coherence ????????: Oracle Solaris 11 ??? 10 ????????? Oracle ???? ISV????????????? SPARC SuperCluster ???????·??????????????????????? ???????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????? ???????????????????? SPARC SuperCluster ??????????????????????????????? ??????????? SuperCluster ?????????????Oracle OpenWorld Tokyo 2012 ????????????????????! 4 ? 5 ?????????????????????????????? Oracle OpenWorld Tokyo 2012 ??????????? SPARC SuperCluster ???????????????? ????????????????? 4/5(?) ????????? G2-01 ?SPARC SuperCluster ????????????????? Ops Center ????????????????(11:50 - 13:20) 4/5(?) S2-42 ???UNIX?????????? - SPARC SuperCluster? (16:30 - 17:15) 4/5(?) S2-53 ?Oracle E-Business Suite?????????????????? ??/??????????????????????”SPARC SuperCluster”?(17:40 - 18:25) ???????????!! Oracle OpenWorld Tokyo 2012 ???? URL http://www.oracle.com/openworld/jp-ja/index.html ?????? 7264 ???????????????

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  • Ideal backup appliance for backup software like Bacula?

    - by Ricket
    I'm at a small company and we (the IT department of two) manage <100 client computers and a handful of servers. Currently we're using a company's appliance to handle backup; it does a small backup every night and a full backup every weekend, and a guy comes on Wednesday to take an offsite backup drive (and gives back last week's drive to swap with it). The backup is done only on the servers' hard drives, because our client computers and employees make sure not to store anything worthwhile on their own computers. So it's a pretty simple situation. Lately this system, mainly the appliance, has been having problems, so we are looking for an alternative. I'm researching other companies but also looking into what we might expect from trying to do this ourselves. There will undoubtedly be a large learning curve, but hey, that's what serverfault is for, right? :) So anyway I was looking at Bacula. Feature list sounds great, documentation is plentiful, but it's only software. So my question is, what is the ideal backup server to run the Bacula server software on? And not only the server but other related appliances. Our current backup appliance uses only hard drives, not tape drives. It has several plugged into it at one time, in hotswap bays on the front of the machine. I couldn't help but notice though, it's hardly more than Windows XP with hard drive bays, a PCI eSATA card (which connects to another appliance extension piece with 2 more bays), and their software. Since the company will take back their appliance if/when we cancel with them, where can I go to configure a server with these kinds of things? And should I consider switching to tape drives? What other concerns should I be thinking about when I pick out hardware for a backup server? Maybe I'm being naive, I'm sure Dell (and any other computer company) sells them in the small business section of their website, but I wanted to make sure that there's not some other more recommended place that other companies are getting their hardware from, and that I don't need anything special for Bacula.

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  • Query total page count via SNMP HP Laserjet

    - by Tim
    I was asked to get hold of the total pages counts for the 100+ printers we have at work. All of them are HP Laser or Business Jets of some description and the vast majority are connected via some form of HP JetDirect network card/switch. After many hours of typing in IP addresses and copying and pasting the relevant figure in to Excel I have now been asked to do this on a weekly basis. This led me to think there must be an easier way, as an IT professional I can surely work out some time saving method to solve this issue. Suffice it to say I do not feel very professional now after a day or so of trying to make SNMP work for me! From what I understand the first thing is to enable SNMP on the printer. Done. Next I would need something to query the SNMP bit. I decided to go open source and free and someone here recommended net-snmp as a decent tool (I would like to have just added the printers as nodes in SolarWinds but we are somewhat tight on licences apparently). Next I need the name of the MIB. For this I believe the HP-LASERJET-COMMON-MIB has the correct information in it. Downloaded this and added to net-snmp. Now I need the OID which I believe after much scouring is printed-media-simplex-count (we have no duplex printers, that we are interested in at least). Running the following command yields the following demoralising output: snmpget -v 2c -c public 10.168.5.1 HP-LASERJET-COMMON-MIB:.1.3.6.1.2.1.1.16.1.1.1 (the OID was derived from running: snmptranslate -IR -On printed-media-simplex-count Unlinked OID in HP-LASERJET-COMMON-MIB: hp ::= { enterprises 11 } Undefined identifier: enterprises near line 3 of C:/usr/share/snmp/mibs/HP-LASER JET-COMMON-MIB..txt .1.3.6.1.2.1.1.16.1.1.1 ) Unlinked OID in HP-LASERJET-COMMON-MIB: hp ::= { enterprises 11 } Undefined identifier: enterprises near line 3 of C:/usr/share/snmp/mibs/HP-LASER JET-COMMON-MIB..txt HP-LASERJET-COMMON-MIB:.1.3.6.1.2.1.1.16.1.1.1: Am I barking up the wrong tree completely with this? My aim was to script it all to output to a file for all the IP addresses of the printers and then plonk that in Excel for my lords and masters to digest at their leisure. I have a feeling I am using either the wrong MIB or the wrong OID from said MIB (or both). Does anyone have any pointers on this for me? Or should I give up and go back to navigationg each printers web page individually (hoping not).

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  • Fatal error 9001 on shared SQL Server 2008

    - by user643192
    I've asked this same question on StackOverflow, but I might actually have a better chance for an answer here so am posting here as well. I know this question has been asked here before, but none of the suggestions have worked for me. I have an ASP.NET MVC (v. 3) website on a shared server. The website was working fine for a few weeks now, until I started getting a Fatal Error 9001 error straight after login. Because this is a shared server, there are only very limited things I can do with the database (and I don't know that much about databases anyway). The help desk insist that there is nothing wrong with their server. I got various suggestions from them: Upgrading to the business plan because I am out of space (first suggestion) Even though the .mdb file is small, the .ldb can grow very quickly. The .ldb file is probably taking up all the space. I have 100MB available, the database size is 16.5MB. Can the .ldb file take up the remaining space? On querying this with the helpdesk, they admitted that my entire db is only 25MB. There is something wrong with my SQL queries and I should check the website. I'm using EF with linq to SQL. Everything was working fine until now... Can there be something that goes wrong in the queries that causes this sort of error? There is nothing wrong to be seen in the db logs, so this error cannot possibly have happened. I should log it next time it happens and contact again. I found some posts suggesting that restoring a DB backup can get rid of the issue. I do not have a recent backup, and can't take a new one because of a fatal error 9001 occurring. Since this is a shared server I have about 0 authority to execute anything against the DB (think CHECKDB, truncating the log, etc.). So I am at my wits end pretty much. What else can I do/try to get my website moving again?

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  • Windows 7 extremely slow login, exchange performance, printer enumeration, etc...

    - by Jeff
    Background: I have a fresh copy of Windows 7 Professional x64 on a Dell Latitude E6500. The laptop has 8GB RAM, 250GB drive, and all Intel peripherals (net/wifi/graphics). All available Windows updates, as well as hardware drivers are installed. The IT folks where I work joined the computer to our Windows 2003-based Active Directory domain. There are no errors in any logs that we've looked at, and Group Policy templates appear to have applied properly. Problem: Every time I turn on or reboot the computer, it takes between 2 to 10 (all times are actual) minutes after successfully typing my username/password to get to my desktop. My login script does not always run. Sometimes I get a black screen, and a couple of minutes later the login script will pop up and take up to 10 minutes to complete. I can get around this by hitting cntrl-shift-esc and running explorer.exe from the Task Manager. The login script continues to hang, but I can minimize it and go on about my business. Either way, it generally throws errors prior to completing. I often get slow or failed connectivity to Exchange via Outlook. When I bring up printer dialogs, they take several minutes to populate, and block the calling app while doing so. Copies to SMB shares are very slow. On my home network, everything works fine. On both the work network and home network, I can use remote internet resources just fine. Web pages pull up, remote VPN's are fine, I can max out bandwidth on SpeakEasy Speed Test. I can get almost max bandwidth transferring FTP/HTTP over a LAN. Another symptom of the problem is that when I first log in, the work network shows as "Identifying" for a long time in the Network and Sharing Center, and will often then change to the name of the work domain, but say "Unauthenticated Network". Note that this computer previously ran Windows Vista with none of these problems. Attempts to Fix: Installed the Win7 admin pack Uninstalled/reinstalled all hardware drivers Verified Active Directory DNS settings (Vista works relatively well on the same network) Reset all TCP/IP settings on all adapters using the netsh commands to do so Disabled ipv6 on all adapters Disable wifi adapter while on work network Locked the network card to 100/Full, 1000/Full; also tried Auto Added various important addresses to hosts file (exchange, dns, ad) -- removed when didn't help My background is a jpeg (sounds unrelated but there is apparently a win7 login bug related to solid color background) More I have forgotten The IT staff at my company indicated they believe this is due to having Windows 2003 AD servers and not having any Windows 2008 R2 AD servers. Other than that, they have no advice or assistance to offer other than a rebuild (already tried that once with similar symptoms), or downgrade to Vista. Any thoughts out there?

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  • Microsoft CRM Dynamics Install

    - by Pino
    Trying to install CRM4.0 on Windows Small Business Server. We get through the isntall process (Setting up database, website, AD etc) when we clikc install though the following error is dumped to the log file, anyone point us in the right directon? 13:49:07| Info| Win32Exception: 1635 13:49:07| Error| Failed to revoke temporary database access.System.Data.SqlClient.SqlException: Cannot open database "MSCRM_CONFIG" requested by the login. The login failed. Login failed for user 'SCHIP\administrator'. at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup) at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) at System.Data.SqlClient.SqlConnection.Open() at Microsoft.Crm.CrmDbConnection.Open() at Microsoft.Crm.Setup.Database.SharedDatabaseUtility.DeleteDBUser(String sqlServerName, String databaseName, String user, CrmDBConnectionType connectionType) at Microsoft.Crm.Setup.Server.RevokeConfigDBDatabaseAccessAction.Do(IDictionary parameters) 13:49:07| Error| HResult=80004005 Install exception.System.Exception: Action Microsoft.Crm.Setup.Server.MsiInstallServerAction failed. --- System.ComponentModel.Win32Exception: This update package could not be opened. Verify that the update package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer update package at Microsoft.Crm.Setup.Common.Utility.MsiUtility.InstallProduct(String packagePath, String commandLine) at Microsoft.Crm.Setup.Server.MsiInstallServerAction.Do(IDictionary parameters) at Microsoft.Crm.Setup.Common.Action.ExecuteAction(Action action, IDictionary parameters, Boolean undo) --- End of inner exception stack trace --- at Microsoft.Crm.Setup.Common.Action.ExecuteAction(Action action, IDictionary parameters, Boolean undo) at Microsoft.Crm.Setup.Common.Installer.Install(IDictionary stateSaver) at Microsoft.Crm.Setup.Common.ComposedInstaller.InternalInstall(IDictionary stateSaver) at Microsoft.Crm.Setup.Common.ComposedInstaller.Install(IDictionary stateSaver) at Microsoft.Crm.Setup.Server.ServerSetup.Install(IDictionary data) at Microsoft.Crm.Setup.Server.ServerSetup.Run() 13:49:07| Info| Microsoft Dynamics CRM Server install Failed. 13:49:07| Info| Microsoft Dynamics CRM Server Setup did not complete successfully. Action Microsoft.Crm.Setup.Server.MsiInstallServerAction failed. This update package could not be opened. Verify that the update package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer update package

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  • Sendmail - Multiple Domains, One Box - Blocking One Or Two Domains

    - by TangoOversway
    I have a number of domains hosted at a web hosting service. They use sendmail to handle incoming email. I have six domains on this service (which we can call aaa.com, bbb.com and so on). Each email account has the same name and one email box. In other words, [email protected], [email protected], [email protected] and all the others go into one box, /var/spool/mail/tango, where my email program on my desktop picks it up. I have done very little work in sendmail. I haven't had to, and I've been warned it's a steep learning curve. But now I'm running into an issue. I was in a business situation where, for years, my email address was on the website for aaa.com. (We won't go into why this was necessary - it wasn't my preference and it's in the past.) Now I'm using [email protected] instead of [email protected]. I was getting about 1,000 or more pieces of spam a day, but SpamAssassin and my own email program caught about 75% of that. (Which still left stuff to delete.) Now, after checking, I see that 90% or more goes to [email protected], the one that was on the web for years. I'd like to deactivate [email protected] and possibly [email protected] and [email protected], but want to keep using [email protected]. Remember, email to tango at any of these domains will go into one email box. I've had people tell me that sendmail can be configured so I can deactivate [email protected] (and other domains) and still use [email protected] (and others, if I want to). In other words, I can configure sendmail to use this account on some domains and not others. One of the people who was teling me this was in tech support at the hosting service. But I wrote to tech support with a work order to do this and now I'm told it can't be done. I can modify config files myself on this account if needed, but I was hoping to just let them do it. (I love delegation -- it means I spend more time doing my stuff.) Is it possible to keep an email account active on one domain and not others with sendmail, when all domains are hosted on the same server? Is there a name for this process or setting? Any information would be helpful - either pointers to instructions so I can do it, or enough info so I can tell tech support, "This is where to look, and it can be done, so please pass my request on to someone who works with sendmail and knows how to do it." Is this something sendmail can do?

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  • What Remote Desktop Solution Do You Use To Service Your Clients' PCs? [closed]

    - by Sootah
    Possible Duplicate: What’s the best Remote Desktop Application? I am the owner of a local computer repair business that primarily services its clients on-site. On the occasions that we do service the machines in the office we generally have one of our techs pick the computer up while they are out and about and bring it back with them. Only rarely will we require the customer to bring us the computer themselves. In order to reduce costs, be much more efficient, and potentially expand our market far beyond what would be feasible with travel required; I am looking at ways that we can service our clients remotely whenever possible. What we're in need of is a solid remote desktop application that will be incredibly easy for our customers to connect to, as well as be robust enough that we don't need the client babysitting the computer during the entire repair. Ideally I would like to use a web-based solution so that we don't have to walk the customers through installing, connecting, and configuring it over the phone. This would be unacceptable because of the level of service they are used to. Effectively we'd want them to be able to just go to a URL, enter a PIN or something, and then they are connected and ready to rumble. (Obviously the option to just email them a link that'd do all this for them would be what we'd be aiming for) Along with the ease of use factor, we would need the product to not require any further intervention on the part of the client after we have connected. Nobody is going to be happy if we have to call them every 15 minutes so they can reconnect to us every time we reboot - so auto-reconnect is an absolute must. The only product I know of right now that does any of this is LogMeIn Rescue. It allows unattended access, the applet is lightweight and installs quickly, and the customer can either enter a PIN on the site or just click a link emailed to them in order to connect. The only real downside I see to LogMeIn Rescue is that it's $120.00/month per technician. While we'd ultimately end up saving far more than that per month just in fuel costs alone, I'd like to explore any other options out there that I may not have come across. Are there any equally good products out there? If so what are they, why do you recommend them, how have you been utilizing them yourself, and what do they cost?

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  • disk-to-disk backup without costly backup redundancy?

    - by AaronLS
    A good backup strategy involves a combination of 1) disconnected backups/snapshots that will not be affected by bugs, viruses, and/or security breaches 2) geographically distributed backups to protect against local disasters 3) testing backups to ensure that they can be restored as needed Generally I take an onsite backup daily, and an offsite backup weekly, and do test restores periodically. In the rare circumstance that I need to restore files, I do some from the local backup. Should a catastrophic event destroy the servers and local backups, then the offsite weekly tape backup would be used to restore the files. I don't need multiple offsite backups with redundancy. I ALREADY HAVE REDUNDANCY THROUGH THE USE OF BOTH LOCAL AND REMOTE BACKUPS. I have recovery blocks and par files with the backups, so I already have protection against a small percentage of corrupt bits. I perform test restores to ensure the backups function properly. Should the remote backups experience a dataloss, I can replace them with one of the local backups. There are historical offsite backups as well, so if a dataloss was not noticed for a few weeks(such as a bug/security breach/virus), the data could be restored from an older backup. By doing this, the only scenario that poses a risk to complete data loss would be one where both the local, remote, and servers all experienced a data loss in the same time period. I'm willing to risk that happening since the odds of that trifecta negligibly small, and the data isn't THAT valuable to me. So I hope I have emphasized that I don't need redundancy in my offsite backups because I have covered all the bases. I know this exact technique is employed by numerous businesses. Of course there are some that take multiple offsite backups, because the data is so incredibly valuable that they don't even want to risk that trifecta disaster, but in the majority of cases the trifecta disaster is an accepted risk. I HAD TO COVER ALL THIS BECAUSE SOME PEOPLE DON'T READ!!! I think I have justified my backup strategy and the majority of businesses who use offsite tape backups do not have any additional redundancy beyond what is mentioned above(recovery blocks, par files, historical snapshots). Now I would like to eliminate the use of tapes for offsite backups, and instead use a backup service. Most however are extremely costly for $/gb/month storage. I don't mind paying for transfer bandwidth, but the cost of storage is way to high. All of them advertise that they maintain backups of the data, and I imagine they use RAID as well. Obviously if you were using them to host servers this would all be necessary, but for my scenario, I am simply replacing my offsite backups with such a service. So there is no need for RAID, and absolutely no value in another layer of backups of backups. My one and only question: "Are there online data-storage/backup services that do not use redundancy or offer backups(backups of my backups) as part of their packages, and thus are more reasonably priced?" NOT my question: "Is this a flawed strategy?" I don't care if you think this is a good strategy or not. I know it pretty standard. Very few people make an extra copy of their offsite backups. They already have local backups that they can use to replace the remote backups if something catastrophic happens at the remote site. Please limit your responses to the question posed. Sorry if I seem a little abrasive, but I had some trolls in my last post who didn't read my requirements nor my question, and were trying to go off answering a totally different question. I made it pretty clear, but didn't try to justify my strategy, because I didn't ask about whether my strategy was justifyable. So I apologize if this was lengthy, as it really didn't need to be, but since there are so many trolls here who try to sidetrack questions by responding without addressing the question at hand.

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  • Why do we get a sudden spike in response times?

    - by Christian Hagelid
    We have an API that is implemented using ServiceStack which is hosted in IIS. While performing load testing of the API we discovered that the response times are good but that they deteriorate rapidly as soon as we hit about 3,500 concurrent users per server. We have two servers and when hitting them with 7,000 users the average response times sit below 500ms for all endpoints. The boxes are behind a load balancer so we get 3,500 concurrents per server. However as soon as we increase the number of total concurrent users we see a significant increase in response times. Increasing the concurrent users to 5,000 per server gives us an average response time per endpoint of around 7 seconds. The memory and CPU on the servers are quite low, both while the response times are good and when after they deteriorate. At peak with 10,000 concurrent users the CPU averages just below 50% and the RAM sits around 3-4 GB out of 16. This leaves us thinking that we are hitting some kind of limit somewhere. The below screenshot shows some key counters in perfmon during a load test with a total of 10,000 concurrent users. The highlighted counter is requests/second. To the right of the screenshot you can see the requests per second graph becoming really erratic. This is the main indicator for slow response times. As soon as we see this pattern we notice slow response times in the load test. How do we go about troubleshooting this performance issue? We are trying to identify if this is a coding issue or a configuration issue. Are there any settings in web.config or IIS that could explain this behaviour? The application pool is running .NET v4.0 and the IIS version is 7.5. The only change we have made from the default settings is to update the application pool Queue Length value from 1,000 to 5,000. We have also added the following config settings to the Aspnet.config file: <system.web> <applicationPool maxConcurrentRequestsPerCPU="5000" maxConcurrentThreadsPerCPU="0" requestQueueLimit="5000" /> </system.web> More details: The purpose of the API is to combine data from various external sources and return as JSON. It is currently using an InMemory cache implementation to cache individual external calls at the data layer. The first request to a resource will fetch all data required and any subsequent requests for the same resource will get results from the cache. We have a 'cache runner' that is implemented as a background process that updates the information in the cache at certain set intervals. We have added locking around the code that fetches data from the external resources. We have also implemented the services to fetch the data from the external sources in an asynchronous fashion so that the endpoint should only be as slow as the slowest external call (unless we have data in the cache of course). This is done using the System.Threading.Tasks.Task class. Could we be hitting a limitation in terms of number of threads available to the process?

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  • Nameserver not resolving or domain not pingable [closed]

    - by Ricky
    Sorry, if anyone can think of a better title please change it! I want to host my own websites from home. For testing purposes, I have a virtual machine running a trial version of Windows Server 2008 Enterprise. Note I currently run a VPS and host my own websites but due to a nice speed upgrade on our line I now want to host from home. I have several domains but I wanted to test with one, that is rickyoleary.com. Our ISP does not provide static IP addresses unless we have a business account so I've been looking at no-ip.com. I admit my networking isn't the best, hence this question but I've been bashing my head all day on this one. I created a host name, muffinbubble.no-ip.org which runs on IP: 86.148.124.15. I've setup IIS on the server with a simple test page. I've then forwarded port 80 traffic from the router and from what I can see, it's working. If I access my website (I was unable to link to this for some reason so please copy and paste this) - http://86.148.124.15/ - I see my test page. So the next step was to create my nameservers. This domain is with namecheap.com so I created my nameservers, ns1.rickyoleary.com and ns2.rickyoleary.com. Both these point to the same IP (and yes, that will be changed after testing), the same IP as above: 86.148.124.15. On the server itself I have set up DNS entries as below which I believe to be correct and added rickyoleary.com and www.rickyoleary.com in the host headers (or bindings) in IIS 7.0. If I try and look up my domain, rickyoleary.com it shows ns1.rickyoleary.com and ns2.rickyoleary.com as the nameservers. I then tried to use just-ping.com on my nameserver ns1.rickyoleary.com. I get 100% packets lost, but the correct IP address is returned (I'm guessing the router does not allow pings, but is still accessible...). I get no response when pinging rickyoleary.com. Here's the problems: I cannot ping ns1.rickyoleary.com or ns2.rickyoleary.com from a command prompt. I'm not sure if this is an issue. When I added the nameservers in Windows Server 2008 and clicked 'resolve' a message box displays stating "No such host is known". I cannot ping rickyoleary.com. rickyoleary.com is not showing my test page on my server. Now - please note, I've waited around 6 hours for propagation. From my experience, although you're told to wait 24 - 48 hours, the changes are normally pretty quick so perhaps I'm being impatient or naive to think it should all be working fine until then. I would really appreciate some help here. Thanks.

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  • Distinction between an extranet and a DMZ

    - by Markus Yrjölä
    I've been reading about intranets, extranets, DMZs and VPNs now, and I'd need some clarifications related to extranets and DMZs. I understand that they are different types of concepts - extranet allows limited access to some intranet resources, while DMZ is a subnet that sits between the internet and intranet and hosts the external-faced services. However, I'd like to know what is their distinction in practice in a usual setup? The Wikipedia article on extranets says that extranets are similar to DMZs because they are used for the same purpose (providing access to some services/resources without exposing the whole intranet). The article also states that an extranet is a part of a VPN, and this TechNet article also states that extranet access is often implemented similarly to remote intranet access, e.g. with a VPN. The TechNet article also says that commonly the extranet is hosted inside the DMZ. This Pearson article says "Although [the DMZ] is technically located within the intranet, [it] can serve as the extranet as well". This is slightly confusing. Consider this scenario: A company has a B2C website hosted in the DMZ. The website can be accessed from anywhere, but requires user authentication. The underlying web app has its database inside the intranet and also interacts with some web services that are hosted inside the intranet (i.e. it accesses intranet resources). The way I see it, the website does effectively offer a restricted access to the intranet. But can it be considered an extranet? If we take the Wikipedia definition of an extranet literally - "An extranet is a computer network that allows controlled access from outside of an organization's intranet" - I think it can. Let's say that the above can't be considered an extranet. What if we change the scenario slightly, and say it's a B2B website, where the access is e.g. limited to connections coming from a specific business partner (by using site-to-site VPN, for example). In this case it surely is an extranet, right? If this is the case, then the difference between extranet services and any other services hosted in the DMZ is simply access restrictions?

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  • Disk operations freeze Debian

    - by Grzenio
    Hi, I have just installed Debian testing on my new desktop and I am not very happy with performance - when I perform a disk intensive operation, e.g. upgrade packages in the system, everything seems to freeze, e.g. changing tabs in Iceweasel takes 3 seconds. I run the Debian on my 3 year old Thinkpad X60 ultra-portable, and I don't have these issues. (every single parameter of the laptop is much worse than the desktop). I am using the default packaged kernel and scripts. I run hdparm -t /dev/sda1 And I got around 96GB/s, which is expected. What else can I try to make it work better? EDIT: grzes:/home/ga# hdparm -i /dev/sda /dev/sda: Model=WDC WD15EARS-00Z5B1, FwRev=80.00A80, SerialNo=WD-WMAVU1362357 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=50 BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=16 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=2930277168 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 AdvancedPM=no WriteCache=enabled Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7 * signifies the current active mode EDIT2: Even my wife said "on this new computer I can't do anything when I copy the photos from the camera and its much worse than on the old one". So it must be serious. EDIT3: Updated to 2.6.32, but still no improvement EDIT4: I forgot to mention that the new disk is ext4, the old was ext3. EDIT5: Still not solved. I have a P43 ASUS P5QL-E board. Lines from dmesg that seem relevant: [ 0.370850] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) [ 0.370852] io scheduler noop registered [ 0.370853] io scheduler anticipatory registered [ 0.370854] io scheduler deadline registered [ 0.370876] io scheduler cfq registered (default) ... [ 0.908233] ata_piix 0000:00:1f.2: version 2.13 [ 0.908243] ata_piix 0000:00:1f.2: PCI INT B -> GSI 19 (level, low) -> IRQ 19 [ 0.908246] ata_piix 0000:00:1f.2: MAP [ P0 P2 P1 P3 ] [ 0.908275] ata_piix 0000:00:1f.2: setting latency timer to 64 [ 0.908316] scsi0 : ata_piix [ 0.908374] scsi1 : ata_piix [ 0.909180] ata1: SATA max UDMA/133 cmd 0xa000 ctl 0x9c00 bmdma 0x9480 irq 19 [ 0.909183] ata2: SATA max UDMA/133 cmd 0x9880 ctl 0x9800 bmdma 0x9488 irq 19 [ 0.909199] ata_piix 0000:00:1f.5: PCI INT B -> GSI 19 (level, low) -> IRQ 19 [ 0.909202] ata_piix 0000:00:1f.5: MAP [ P0 -- P1 -- ] [ 0.909228] ata_piix 0000:00:1f.5: setting latency timer to 64 [ 0.909279] scsi2 : ata_piix [ 0.909326] scsi3 : ata_piix [ 0.910021] ata3: SATA max UDMA/133 cmd 0xb000 ctl 0xac00 bmdma 0xa480 irq 19 [ 0.910024] ata4: SATA max UDMA/133 cmd 0xa880 ctl 0xa800 bmdma 0xa488 irq 19 [ 0.915575] FDC 0 is a post-1991 82077 ... [ 1.716062] ata1.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [ 1.716074] ata1.01: SATA link down (SStatus 0 SControl 300) [ 1.724318] ata1.00: ATA-8: WDC WD15EARS-00Z5B1, 80.00A80, max UDMA/133 [ 1.724322] ata1.00: 2930277168 sectors, multi 16: LBA48 NCQ (depth 0/32) [ 1.740339] ata1.00: configured for UDMA/133 [ 1.740428] scsi 0:0:0:0: Direct-Access ATA WDC WD15EARS-00Z 80.0 PQ: 0 ANSI: 5 [ 1.746788] scsi 6:0:0:0: CD-ROM ASUS DRW-1608P 1.17 PQ: 0 ANSI: 5 ... [ 1.925981] sd 0:0:0:0: [sda] 2930277168 512-byte logical blocks: (1.50 TB/1.36 TiB) [ 1.926005] sd 0:0:0:0: [sda] Write Protect is off [ 1.926007] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00 [ 1.926020] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [ 1.926092] sda:sr0: scsi3-mmc drive: 40x/40x writer cd/rw xa/form2 cdda tray [ 1.931106] Uniform CD-ROM driver Revision: 3.20 [ 1.931191] sr 6:0:0:0: Attached scsi CD-ROM sr0 ... [ 1.941936] sda1 sda2 sda3 sda4 < sda5 sda6 > [ 1.967691] sd 0:0:0:0: [sda] Attached SCSI disk [ 1.970938] sd 0:0:0:0: Attached scsi generic sg0 type 0 [ 1.970959] sr 6:0:0:0: Attached scsi generic sg1 type 5 ... [ 2.500086] EXT4-fs (sda3): mounted filesystem with ordered data mode ... [ 7.150468] EXT4-fs (sda6): mounted filesystem with ordered data mode

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  • Why do I need to set up Autologon values in registry twice in before it works and can I fix this?

    - by jJack
    Background: As part an automated testing suite I am building, I need to set up Autologon on my virtual machines 'on demand'. By on demand, I mean that I don't want to necessarily pre-configure my VM or any snapshot to have Autologon set up already, for security reasons and also a huge business case. My solution so far: I'm copying a script to the guest machine and then using Sysinternals PsExec to execute it. The script is: reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon" /f /v DefaultUserName /t REG_SZ /d myusername reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon" /f /v DefaultPassword /t REG_SZ /d myfakepassword reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon" /f /v DefaultDomainName /t REG_SZ /d mydomain reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon" /f /v ForceAutoLogon /t REG_SZ /d 1 reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon" /f /v AutoAdminLogon /t REG_SZ /d 1 reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\AutoLogonChecked" /f /ve /d 1 Note: I don't believe AutoLogonChecked is required for machines post Windows 2000 but I'm doing it just in case for now. Maybe ForceAutoLogon isn't either, not sure yet. The Problem: I see PsExec executes this properly and all the values are in the registry, however when I restart the machine, the user isn't automatically logged on...When I run this a second time then restart the machine, the user is finally logged on. A diff between the registry states shows that the first time I run this, it is missing both the "1" for AutoAdminLogon, and also the DefaultPassword key. The second time I execute it, these values are correctly intact as I intended. So, what is going on here? Is this expected? This post claims in the end that it really all just works (the problem was that a logoff script was setting off the values). Doesn't seem to work for me however. Note this seems unique to Windows 7, does not occur in Windows XP Also note that you don't need PsExec to recreate the issue - just modify the registry yourself EDIT/update: Login interactively and run script (so, not executing it remotely), logging off automatically logs me back in (so, it works) remotely execute the script in guest when I'm interactively logged in, logging off automatically logs me back in (so, it works) remotely execute the script in guest when with non-interactive session if I log in afterwards (so, interactive now) then back off, it logs me back in (so, it then works) EDIT/update 2: This only occurs for Win7x86, Win7x64, Win8x64. This does not occur for Windows XP

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  • Messages stuck in SMTP queue - Exchange 2003

    - by Diav
    I need your help people ;-) I have a problem with messages coming into our Exchange Server and ones going out through it. Basically, the messages are stuck in the SMTP queue. A message will come into the server, I can see it listed under "Exchange System Manager", but if you list the properties of the message queue it says something like 00:10 SMTP Message queued for local delivery 00:10 SMTP Message delivered locally to [email protected] 00:10 SMTP Message scheduled to retry local delivery 00:11 SMTP Message delivered locally to [email protected] 00:11 SMTP Message scheduled to retry local delivery etc etc For outgoing message list looks like this: 10:55 SMTP: Message Submitted to Advanced Queuing 10:55 SMTP: Started Message Submission to Advanced Queue 10:55 SMTP: Message Submitted to Categorizer 10:55 SMTP: Message Categorized and Queued for Routing 10:55 SMTP: Message Routed nad Queued for Remote Delivery And the end - since then status didn't change, message is in queue, I am forcing connection from time to time but without an effect. I checked connection with smarthost (used telnet for that) and everything seems to work correctly, so the problem is probably on exchange side. I am using Exchange Server 2003 running on Small Business Server 2003. I don't have any antivirus installed on server. Remaining free space on each partition is over 3Gb, on partition with data bases - it is over 12Gb. All was working good and without problems since 2005, problems started in half of this june - messages started going out and being stuck almost randomly (I don't see a pattern yet, some are going out, some are not, some are going after several hours). I don't know what to do, what to check more, so please, any ideas? Best regards, D. edit Priv1.edb has 14,5GB and priv1.stm 2,6GB - together those files have more than 16GB - can it be the reason? If yes, then what? Indeed, I haven't thought that it can have something in common with my problem, but several users reported recent problems with Outlook Web Access - they can log in, they see the list of their mails, but they can't see the content of their emails. Although when they are connecting with Outlook 2003/2007 - there is no such problem, only with OWA there is. edit2 So,.. It works now, and I have to admit that I am not really sure what the problem was (hope it won't come back). What have I done: Cleaned up some mailboxes to reduce size of them Dismounted Information Store Defragmentated data base files ( I used eseutil: c:\program files\exchsrvr\bin eseutil /d g:\data base\Exchsrvr\MDBDATA\priv1.edb ) Mounted Information Store back ..and before I managed to do anything else - my queue started moving, elements which were kept there already for days - started moving and after few minutes everything was sent, both, outside and locally. But: priv1.edb is still big (13 884 203 008), priv1.stm as well (2 447 384 576), so this is probably not the issue of size of the file. And if not this, so what was that? And if that was issue of size of the file, then soon it will repeat - is there something I can do to avoid it ?

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  • What "pieces" are needed in order to set up a cluster of physical servers?

    - by Chris Dutrow
    Background: Currently, we use Rackspace cloud servers. We have no intention to stop using them, but would like to look into setting up a cluster of physical servers (probably desktop computers in the $400 range with 8gb memory each) to offset some of our load and work as a secondary, more powerful, less reliable system. To put things in perspective, we can buy comparable desktop computers for the same price as we pay in one month to rent them on Rackspace Cloud. I understand that this is generally a dumb idea. However, in this particular instance, the server cluster is needed for its computation power. It is not mission-critical, it does not host a consumer-facing website, and if it goes down for a day or two, its not really a problem. Currently, we have access to business class verizon fios. If I understand correctly, we can get at least 25 dedicated IP addresses with this service, this should be enough. Requirements: Each server runs Linux Centos 6.3 Some of the servers run Python and execute processes from a task queue (Redis or RabbitMQ) Some of the servers are capable of serving static files and Python driven REST APIs Some of the servers host a Cassandra database cluster One or more of the servers are a Redis database servers One or more of the servers are PostgreSQL servers Questions: What kind of router or switch is needed? We would like the computers to be able to communicate effectively with each other via internal IP addresses. This is especially important for communicating with servers hosting Redis that need to be able to respond to requests very quickly. Are there special switches or routers that need to be used to connect the servers together? Are Desktop computers ok for this? We have found that we are mostly RAM-bottle necked, I understand that some servers have highly superior CPUs, but I'm not sure we need CPU power as much as we need RAM, which is cheap in Desktop computers. Will we have problems with the WIFI cards in the desktops or any other unexpected hardware limitation? What tools should be used to "image" the servers. For example, when we get an installation right for a Redis server or Cassandra node, are there tools that come with Linux Centos 6.3 to image the server to a USB drive or something like that? Or do we need to use some other software for this? What other things are we missing that we should be concerned about? Thanks so much!

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  • Yahoo Webmail - Garbled Quote Text

    - by baultista
    I've encountered a very strange problem when trying to reply to e-mail via my Yahoo Web Mail from a family member's computer. She received an e-mail from a client who is using Microsoft Outlook. When I receive the message it looks perfectly fine in my browser and I can read it. However, when I try to reply to the e-mail the quoted text looks as such: > #yiv9181642880 p.yiv9181642880msonormal1114, #yiv9181642880 > li.yiv9181642880msonormal1114, #yiv9181642880 > div.yiv9181642880msonormal1114 > {margin-right:0in;margin-left:0in;font-size:12.0pt;} > #yiv9181642880 p.yiv9181642880msoacetate1114, #yiv9181642880 > li.yiv9181642880msoacetate1114, #yiv9181642880 > div.yiv9181642880msoacetate1114 > {margin-right:0in;margin-left:0in;font-size:12.0pt;} > #yiv9181642880 p.yiv9181642880emailquote1114, #yiv9181642880 > li.yiv9181642880emailquote1114, #yiv9181642880 > div.yiv9181642880emailquote1114 > {margin-right:0in;margin-left:0in;font-size:12.0pt;} > #yiv9181642880 p.yiv9181642880msochpdefault1114, > #yiv9181642880 li.yiv9181642880msochpdefault1114, > #yiv9181642880 div.yiv9181642880msochpdefault1114 > {margin-right:0in;margin-left:0in;font-size:12.0pt;} > #yiv9181642880 p.yiv9181642880msonormal53, #yiv9181642880 > li.yiv9181642880msonormal53, #yiv9181642880 > div.yiv9181642880msonormal53 > {margin-right:0in;margin-left:0in;font-size:12.0pt;} It's the strangest thing. It doesn't happen with all e-mails except this particular one. At a glance it almost looks like raw CSS code that's being displayed, but I really can't understand why. So far I have tried the following: Try a different browser, both IE11 and Google Chrome Check the browser encoding settings Check Yahoo Web Mail's encoding/font settings My only other guess is that the client used some weird font or formatting on the e-mail that is throwing the message body out of sync. Unfortunately for my family member, she is a contractor working with a medium-sized company that refuses to provide her with a domain e-mail address, so she is forced to conduct business this way. Simply asking the sender to use a more widely supported font wouldn't be an acceptable solution here. Any thoughts?

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  • Encrypted off-site data storage

    - by Dan
    My business has a rather unique problem. We work in China and we want to implement a file server paradigm which does not store any files locally, but rather in a server overseas. Applications would be saved onto our local machines, but data would be loaded directly into memory from the cloud, e.g. I load a docx into word at the beginning of the day, saving periodically to the cloud as I work on it, and turn off my computer at night, with nothing saved locally. Considering recent events, we worry about being raided by the Chinese authorities, and although all our data is encrypted, it would not be hard for the authorities to force us to give up the keys. So the goal is not to have anything compromising physically in China. We have about 20 computers, and we need an authenticated, encrypted connection with this overseas file server. A system with Active-Directory-like permissions would be best, so that only management can read or write to certain files, or workers can only access files that relate to their projects, and to which all access can be cut off should the need arise. The file server itself would also need to be encrypted. And for convenience, it would be nice if this system was integrated with each computer's file explorer (like skydrive or dropbox does, but, again, without saving a copy locally), rather than through a browser. I can't find any solution online. Does anyone know of a service that does this? Otherwise I'll have to do it myself (which kinda sounds fun, but I don't really have the time), and I'm not sure where to start. Amazon maybe. But the protocols that offices would use on their intranet typically aren't encrypted; we need all traffic securely tunneled out of the country. Each computer already has a VPN to a server in California, but I'm unsure whether it would be efficient to pipe file transfers through it. Let me know if anyone has any ideas. And this is my first post; feel free say whether this question is inappropriate/needs to be posted elsewhere.

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  • Linux not buffering block I/O when the device is not "in use" (i.e. mounted)

    - by Radek Hladík
    I am installing new server and I've found an interesting issue. The server is running Fedora 19 (3.11.7-200.fc19.x86_64 kernel) and is supposed to host a few KVM/Qemu virtual servers (mail server, file server, etc..). The HW is Intel(R) Xeon(R) CPU 5160 @ 3.00GHz with 16GB RAM. One of the most important features will be Samba server and we have decided to make it as virtual machine with almost direct access to the disks. So the real HDD is cached on SSD (via bcache) then raided with md and the final device is exported into the virtual machine via virtio. The virtual machine is again Fedora 19 with the same kernel. One important topic to find out is whether the virtualization layer will not introduce high overload into disk I/Os. So far I've been able to get up to 180MB/s in VM and up to 220MB/s on real HW (on the SSD disk). I am still not sure why the overhead is so big but it is more than the network can handle so I do not care so much. The interesting thing is that I've found that the disk reads are not buffered in the VM unless I create and mount FS on the disk or I use the disks somehow. Simply put: Lets do dd to read disk for the first time (the /dev/vdd is an old Raptor disk 70MB/s is its real speed): [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 36.8038 s, 71.2 MB/s Buffers: 14444 kB Rereading the data shows that they are cached somewhere but not in buffers of the VM. Also the speed increased to "only" 500MB/s. The VM has 4GB of RAM (more that the test file) [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.16016 s, 508 MB/s Buffers: 14444 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.05727 s, 518 MB/s Buffers: 14444 kB Now lets mount the FS on /dev/vdd and try the dd again: [root@localhost ~]# mount /dev/vdd /mnt/tmp [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 4.68578 s, 559 MB/s Buffers: 2574592 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 1.50504 s, 1.7 GB/s Buffers: 2574592 kB While the first read was the same, all 2.6GB got buffered and the next read was at 1.7GB/s. And when I unmount the device: [root@localhost ~]# umount /mnt/tmp [root@localhost ~]# cat /proc/meminfo | grep Buffers Buffers: 14452 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.10499 s, 514 MB/s Buffers: 14468 kB The bcache was disabled while testing and the results are same on faster (newer) HDDs and on SSD (except for the initial read speed of course). To sum it up. When I read from the device via dd first time, it gets read from the disk. Next time I reread it gets cached in the host but not in the guest (thats actually the same issue, more on that later). When I mount the filesystem but try to read the device directly it gets cached in VM (via buffers). As soon as I stop "using" it, buffers are discarded and the device is not cached anymore in the VM. When I looked into buffers value on the host I realized that the situation is the same. The block I/O gets buffered only when the disk is in use, in this case it means "exported to a VM". On host, after all the measurement done: 3165552 buffers On the host, after the VM shutdown: 119176 buffers I know it is not important as the disks will be mounted all the time but I am curious and I would like to know why it is working like this.

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  • Is there a way to permanently arrange 2 displays under XP?

    - by rumtscho
    When I am home or on a business trip, or on a meeting, I use my laptop in the usual way. When I get to work, I put it on the docking station and boot it with the lid closed. The image appears on the two displays connected to the docking station. On the left, there is an old monitor connected over VGA, on the right, a big widescreen connected over DVI. Obviously, the videocard seems to think that the DVI is the primary output, and the VGA the secondary one. Thus Windows always displays the widescreen on the left and the old FSC monitor on the right. So when I want to move the mouse pointer from the (physically) left display to the (physically) right display, I have to move it from right to left, which is a usability nightmare. Of course, I can just drag one display over the other one in the display properties, and then everything is as it should be. The catch: Windows remembers this only as long as it has the two displays. Every time it runs on the laptop display, it forgets the setting. Physically switching the monitors isn't an option, for ergonomical reasons. I prefer to run the more important applications on the bigger screen with the better colourspace, and the shape of my desk forces me to sit off-center, so the more important applications should be shown on the right display. Just switching the video ports doesn't help either. When I connect the big monitor over VGA, image quality deteriorates visibly. So what I do now is: every time I bring the laptop to my desk, I boot it. I wait the whole 7 minutes of XP booting, syncing network drives, etc. Then I fire up the display properties, switch to the last tab, drag the widescreen display to the right, and close. Only then can I start working. Does someone have a better idea? The laptop is a Dell Latitude 630 with Windows XP SP 3. It has an nVidia graphics card (not an onboard chip).

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  • Amusing or Sad? Network Solutions

    - by dbasnett
    When I got sick my email ended up in every drug sellers email list. Some days I get over 200 emails selling everything from Viagra to Xanax. Either they don't know what my condition is or they are telling me you are a goner, might as well chill-ax and have a good time. In order to cut down on the mail being downloaded I thought I would add all of the Junk email senders from Outlook to my Network Solution mail server. Much to my amazement I could not find that import Spammers button, so I submitted a tech support request. Here is the response: Thank you for contacting Network Solutions Customer Service Department. We are committed to creating the best Customer experience possible. One of the first ways we can demonstrate our commitment to this goal is to quickly and efficiently handle your recent request. We apologize for any inconvenience this might have caused you. With regard to your concern, please be advised that we cannot import blocked senders in to you e-mail servers. An alternative option is for you to create a Custom Filter that filters unwanted e-mails. To create a Custom Filter: Open a Web browser (e.g., Netscape, Microsoft Internet Explorer, etc.). Type mail.[domain name].[ext] in the address line. Login to your Network Solutions email account. Click on the Configuration left menu tab. Click on the Custom Filter link. Type the rule name. blah, blah, blah Basically add them one at a time. "We are committed to creating the best Customer experience possible." No you are not. You are trying to squeeze every nickle you can out of me. "With regard to your concern, please be advised that we cannot import blocked senders in to you e-mail servers." Maybe I should apply for a job to write those ten complicated lines of code... Maybe I should question my choice of vendors, because if they truly "cannot" then they are to stupid to have my business. It is both amusing and sad. I'll be posting this in every forum I am a member of.

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  • Ubuntu 12 crashed and took down network

    - by Leopd
    We recently set up a new Ubuntu 12.04LTS server on our network. It's not fully configured so it's not doing much beyond sshd and a default apache2 install. But this evening it appears to have crashed. It wasn't responding to the network or the keyboard. But the worst part is, it took down the entire network. My knowledge of the network stack below OSI layer 3 is very limited, so the rest confuses me. When this machine was physically connected to the network, no other machine could connect to the outside internet. When things were broken, running arp showed that our gateway's IP address (10.0.1.1) was listed as "invalid." Unplugging the server from the network fixed the problem, and plugging it back in broke it again. So the crashed server was advertising itself as owning the gateway's IP address? There's nothing at all in syslog during the time when it was causing problems. Any ideas about how to figure out what went wrong or what we can do to prevent it from happening again? I'm hesitant to even put the machine back on the network right now. Update ** It crashed again, and I ran tcpdump -penn arp (thanks bahamat!) for several minutes and got this... (timestamps and duplicate lines removed) 00:1e:65:f8:dc:24 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 10.0.1.1 tell 10.0.2.191, length 46 00:1e:65:f8:dc:24 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 10.0.1.44 tell 10.0.2.191, length 46 60:d8:19:d4:71:d6 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 10.0.1.1 tell 10.0.2.125, length 46 d4:9a:20:04:e9:78 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 192.168.1.1 tell 192.168.1.100, length 28 Update 2 ** When the network is functioning properly, arping -c4 10.0.1.1 returns this: ARPING 10.0.1.1 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=0 time=267.982 usec 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=1 time=422.955 usec 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=2 time=299.215 usec 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=3 time=366.926 usec --- 10.0.1.1 statistics --- 4 packets transmitted, 4 packets received, 0% unanswered (0 extra) When the bad server is plugged in, arping -c4 10.0.1.1 returns: ARPING 10.0.1.1 --- 10.0.1.1 statistics --- 4 packets transmitted, 0 packets received, 100% unanswered (0 extra) Context ** 10.0.x.x is the main subnet. 10.0.1.1 is the main internet gateway 10.0.1.44 is a printer 10.0.2.* devices are all laptops / workstations I have no idea what's using the 192.168.x.x subnet -- your guesses are at least as good as mine. A VM on a workstation? A misconfigured WAP? Somebody re-sharing wifi? A machine that failed to DHCP? The offending ubuntu server's MAC address ends in cd:80 so isn't listed in the dump. It should DHCP to 10.0.3.3 Thanks for any help. This ARP stuff is all voodoo to me. Packets just go to IP addresses, right? ;)

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  • mobile broadband recommendations for Lenovo T500

    - by Justin Grant
    I use a Lenovo T500 primarily in and around San Francisco, although I do some travel in the US on business and occasionally to Europe/Asia. I'm looking for a good mobile broadband option for my T500. I am admittedly baffled by the various mobile-broadband choices (3G vs. 4G, WiMax vs. LTE vs. MIMO vs. ..., etc.). My priorities are (in this order): Compatible with Lenovo T500 and Windows 7. I realize only the AT&T accessory card is listed on Lenovo's site, but I've also heard that other cards will work in my T500 too, like the WiMax/Wifi combo card-- so I'm interested in what actually works, not necessarily only what Lenovo is promoting. Reliable coverage in US large cities, especially the SF Bay Area. my IPhone has lousy coverage in many spots, so I'd be nervous about an AT&T 3G option unless the problem is with the IPhone and not AT&T's network. I'm OK with non-great coverage outside major US cities, since I don't do much travel in those areas. Speed. faster is better. Internal card. I'd slightly prefer something I could install inside my T500 instead of a dongle on the side that might break off, although this is my lowest priority so it's not a big deal. Price. I don't want to pay over $100/month. I've tried lots of Googling and haven't come up with clear answers. I've seen lots of general overviews without recommendations, and lots of passionate opinions which don't feel objective (and don't help me understand compatibility with my hardware & geography). Can you recommend a good, objective guide online, ideally for Lenovo although general guide is OK too, which can help me figure out which option is the best one for me? I'd also be interested in your own personal experiences of using mobile broadband using a Lenovo T500. I'll accept the answer which gets me closest to making a decision.

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  • Add a small RAID card? Will it help overall stability and performance of my nine hard drives?

    - by Ray
    Hi, Will I get any extra genuine added performance and RAID stability if I insert a basic RAID card into a PCI-E x1 slot? I am considering the Adaptec 1220SA - 2 port SATA , pci-express (1x) , raid 0/1. Ok it only supports two SATA drives. Purpose is to help support the eight internal hard drives (1TB each), a DVD drive and an external e-SATA connected 2TB hard drive - by dealing with two of the internal hard drives. My current configuration of eight internal 1TB Barracuda (7200.12) SATA hard drives, one external 2TB SATA Western Digital Green Drive (e-SATA) and one DVD drive can already be supported by the Intel P55 & JMicron controllers on the ASUS motherboard : the Intel P55 (controls six HDD; configured as three x RAID 1), and the JMicron (controls two HDD as one RAID 1, as well as the DVD drive and the external SATA drive via the motherboard's e-SATA port (controlled by the JMicron)). Bigger picture details : I have an ASUS motherboard designed for the LGA1156 type processor and it includes the Intel P55 Express Chipset and JMicron. I am using the Intel Core i7-870 processor, and have 8GB DDR3 (1333) memory (four x 2GB Corsair DIMMs). Enough overall power. The power supply is more than sufficicient for the system. Corsair AX850. The system will never need the full 850 watts (future : second graphics card). The RAID card would provide hardware RAID 1 for two of the eight intrnal drives. It would either reduce the load on : the Intel P55 firmware RAID support, or replace the JMicron controller's RAID 1 set. I am busy installing the above configuration using Windows 7 Ultimate 64-bit as the OS. The RAID card is a last minute addition to the plan. Is it worth spending the extra R700 - R900 on the Adaptec 1220SA, or equivalent RAID card? I cannot afford to spend yet another R2000 - R3000 on a RAID card that would support many SATA2 hard drives, with a better RAID, example the RAID 5. My Issue & assumption : I am trusting that the Intel P55 chipset can properly handle six drives, configured as three * RAID 1. I am assuming that the JMicron can handle, using its RED SATA ports, one RAID-1 (two HDDs). The DVD drive connects to the JMicron optical SATA port 1 (white port 1). White port 2 is not used. The e-SATA connection is from the JMicron straight to, and through the motherboard - to an on-board (rear panel) e-SATA port. Am I being a little hopeful in only using the on-board Intel P55 and the JMicron? Is it a waste of money to install a RAID card that handles two SATA2 drives? OR Is it wisdom to take the pressure a little off the Intel P55? Obviously I am interested in data security, hence RAID 1, not RAID Zero. RAID 5 would be nice. The CPU, Intel Core i7-870 will provide the clout. Context to nine drives : I am using virtualisation with Windows 7 Ultimate. Bootable VMs. The operating system gets a mirror. Loaded apps gets a mirror. The current design data is kept in another mirror and Another mirror is back-up one and / or VM territory. Then the external 2TB drive (via e-SATA) is the next layer of data security and then finally, I use off-site data security. Thanks.

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