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• Windows desktop virutalization instead of replacing work stations

  - by Chris Marisic

  I'm head of the IT department at the small business I work for, however I am primarily a software architect and all of my system administration experience and knowledge is ancillary to software development. At some point this year or next we will be looking at upgrading our workstation environment to a uniform Windows 7 / Office 2010 environment as opposed to the hodge podge collection of various OEM licensed editions of software that are on each different machine. It occurred to me that it is probably possible to forgo upgrading each workstation and instead have it be a dumb terminal to access a virutalization server and have their entire virtual workstation hosted on the server. Now I know basically anything is possible but is this a feasible solution for a small business (25-50 work stations)? Assuming that this is feasible, what type of rough guidelines exist for calculating the required server resources needed for this. How exactly do solutions handle a user accessing their VM, do they log on normally to their physical workstation and then use remote desktop to access their VM, or is it usually done with a client piece of software to negotiate this? What types of software available for administering and monitoring these VM's, can this functionality be achieved out of box with Microsoft Server 2008? I'm mostly interested in these questions relating to Server 2008 with Hyper-V but fell free to offer insight with VMware's product line up, especially if there's any compelling reasons to choose them over Hyper-V in a Microsoft shop. Edit: Just to add some more information on implementation goals would be to upgrade our platform from a Win2k3 / XP environment to a full Windows 2008 / Win7 platform without having to perform any of that associated work with our each differently configured workstation. Also could anyone offer any realistic guidelines for how big of hardware is needed to support 25-50 workstations virtually? The majority the workstations do nothing except Office, Outlook and web. The only high demand workstations are the development workstations which would keep everything local.

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• Trouble printing to local printer when connected to VPN with split-tunneling enabled

  - by Marve

  I'm a volunteer network admin for a multi-tenant non-profit office space. One of our new tenants uses a VPN to connect to remote resources using RRAS and Small Business Server 2008. They also have a local network printer for the workstations in our office. When connected to the VPN, they cannot print to the local printer. I informed their network admin that they need to enable split-tunneling to fix this. Their network admin enabled split-tunneling, but apparently printing still didn't work. He told me that I need to open port 1723 on our office firewall to allow it to work. I'm just a novice administrator and not familiar with RRAS, but this doesn't sound right to me and I haven't been able to find anything on the web to validate it. Additionally, my understanding of split-tunneling is that it is handled entirely by the VPN client and should work irrespective of firewall settings. Is my understanding of the situation incorrect? What steps should I take to resolve this problem?

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• Help, my CentOS servers keep going down , No route to host after a random uptime

  - by user249071

  Hello , I have a couple of Centos linux servers, that have a very simple task, they run nginx + fastcgi for php , and some NFS mounts between them, readonly They have some RPC commands to start some downloading processes with wget, nothing fancy , from a main server, but their behavior is very unstable, they simply go down, we tried to monitor ram , processor usage, even network connections, they don't load up so much, max network connections up to... 250 max, 15% processor usage and memory , well, doesn't even fill up, 2.5GB from 8GB max , I have no ideea why can a linux server go down like that, they aren't even public servers, no domain names installed no public serving, for sites. The only thing that I've discovered was that if i didn't restart the network service every couple of hours or so... the servers were becoming very slow, starting apps very slow, but not repoting a high usage of resources...Maybe Centos doesn't free the timeout connections, or something like that...It's based on Red Hat right? I'm not a linux expert , but I'm sure that there are a few guys out there that can easily have an answer to this , or even have some leads to what i can do ... I haven't installed snort, or other things to view if we have some DOS attacks, still the scheduled script that restarts the network each hour should put the system back online, and it doesn't.... Thank you in advance

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• SQL Server performance on VSphere 4.0

  - by Charles

  We are having a performance issue that we cannot explain with our VMWare environment and I am hoping someone here may be able to help. We have a web application that uses a databases backend. We have an SQL 2005 Cluster setup on Windows 2003 R2 between a physical node and a virtual node. Both physical servers are identical 2950's with 2x Xeaon x5460 Quad Core CPUs and 64GB of memory, 16GB allocated to the OS. We are utilizing an iSCSI San for all cluster disks. The problem is this, when utilizing the application under a repeated stress testing that adds CPUs to the cluster nodes, the Physical node scales from 1 pCPU to 8 pCPUs, meaning we see continued performance increases. When testing the node running Vsphere, we have the expected 12% performance hit for being virtual but we still scale from 1 vCPU to 4 vCPUs like the physical but beyond this performance drops off, by the time we get to 8 vCPUs we are seeing performance numbers worse than at 4 vCPUs. Again, both nodes are configured identically in terms of hardware, Guest OS, SQL Configurations etc and there is no traffic other than the testing on the system. There are no other VMs on the virtual server so there should be no competition for resources. We have contacted VMWare for help but they have not really been any suggesting things like setting SQL Processor Affinity which, while being helpful would have the same net effect on each box and should not change our results in the least. We have looked at all of VMWare's SQL Tuning guides with regards to VSphere with no benefit, please help!

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• Hard drive degredation from large memory usage and paging files?

  - by Stephen R

  I've had a question(s) regarding computer degradation going through my head for a while and haven't found many good resources for researching it. 1) First off, when is the virtual RAM/paging file on a hard drive used by Windows? Is it used when the RAM is full? Or does it use the Virtual RAM/paging file as intermediate caching between the RAM and actual hard drive space all the time? 2) If I were to run many applications on my computer at the same time and have a bad habit of doing this for the entire lifetime of the computer, does it use more of the virtual RAM/paging file than if I were to have fewer programs running? Just to note, the RAM never fills up on my computer but it is used heavily. 3) By extension of question 2, if the virtual RAM/paging file is used more heavily, would that result in rapid hard drive degradation? I have seen a pattern among all of the computers that I have owned or used in the past 5 years. I am the kind of person to leave my web browser up with 40 tabs among other programs which will eat up 40% of my memory typically. Over time my computer will slow down, browsers start crashing, programs start seizing up or crashing themselves, eventually the computer becomes essentially unusable. I have been trying to rack my mind to come up with a solution other than to purchase a new PC to have it die on me in the next couple years as well. This is the only thought that has come to mind that might have a simple hardware fix...Windows ReadyBoost...Maybe? I'd like to be able to discuss this so I can learn something about all of the above. Thanks.

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• Mavericks permission issues with Windows Server deduplicated shares

  - by dmohlmaster

  We have a number of 10.9-10.9.3 - Mavericks - machines installed throughout our facility. Much of the user content is pulled from shares stored on our Windows Server 2012 fileservers with deduplication enabled. I have found that files newly written or unoptimized are able to be accessed without issue - read, written, modified, etc. Once the file gets optomized/deduplicated and Windows adds the P & L attributes - sparse and symlink - the Macs running Mavericks begin to have access issues. Once the files get deduplicated, users begin receiving read access errors when copying files (see error1 below). This happens when copying to folders within the current folder tree or copying somewhere to the local system. If you 'stop' the copy operation and retry a few more times, it may eventually work for the specific instance but fail again later. I am however, able to copy these files without issue via the terminal. Other systems running 10.7 do not experience the same issues and are able to access file server resources without issue. Many of the systems having issues are newer and thus not able to be downgraded to 10.8 or 10.7. I have tried finder replacements such as Pathfinder but the results are the same. I know this is at least similar to the issues many Mac users are already experiencing and posting about but I haven't seen it directly linked to deduplication and the attributes written by Windows server. Has anyone seen this issue? Have any solutions been found? Error 1: When copying files after the PL attributes have been set by deduplication. "One or more items can't be copied to "Foler" because you don't have permissions to read them. ******************************************' Via the system.log, I am also seeing the following error when accessing these deduplicated file shares. The reparse point tag listed below is "IO_REPARSE_TAG_DEDUP" Reported error: "smbfs_nget: filename.ext - unknown reparse point tag 0x80000013"

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• Switched from DVI to HDMI, possible audio artifacts?

  - by I take Drukqs

  I'm using an ASUS VH236H monitor and an EVGA GeForce 570 GTX both of which are brand new. My monitor has an audio out port for speakers/headphones so I plugged in my headphones and made a random selection from my library when I noticed two things: There are static-like artifacts during "louder" parts of songs. There's what seems to be a volume cap in place. When I crank the volume past 100% in VLC the decibel level does not truly increase but the amount of static does. The cable is not new; I yanked it off of my PS3 when my DVI cable broke. It has been used a good amount on my HDTV and PS3 so I doubt it's a matter of burn-in. I like the way the setup works with an HDMI cable as opposed to DVI because my headphones barely reach my rig whereas I have plenty of slack when they're plugged into my monitor. Thanks in advance for any support. Note: I'm using a high quality HDMI cable from monoprice, AKG K702 headphones, and VLC media player.

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• Java: very slow tomcat and too big war file

  - by NaN

  I created some sort of RESTful API backend for a mobile app. It's written completely in Java using Jersey as Framework. At the moment no database is used, it's all in the memory, but this is no problem so far (it's only for prototyping purposes). I ordered the smallest package from digital ocean and installed tomcat7. All in all tomcat works, but I have three major problems: 1) It takes a long time until tomcat deploys the app: I deploy it per tomcat manager and it takes about 2 minutes unit the site works (excl. war upload time). 2) The war files are quite big (16MB): I don't know why they are so big. There are no database dependencies and most logic is written in plain java. Okay, we are using jersey, but 16MB are a lot for the logic of a small webservice. 3) I have to restart tomcat all 3 days or so. It looks like a memory leak or something similar. If the app runs for a few days the response time is quite high and the server seems to be frozen. It works again, if I restart tomcat per ssh. You can find my mvn pom file right here. Do you have some tips? Are there good tomcat alternatives?

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• Windows Server 2008 R2 running at a snail's pace

  - by Django Reinhardt

  Really weird problem here. Our main web server has started running at a snail's pace, for absolutely no reason we can discern. Even after restarting the machine, when there's no little or no ram usage and CPU usage is fluctuating between 0 and 30%, simple tasks, like opening Internet Explorer, or waiting for My Computer to open, take forever. There are no processes hogging system resources that we can see... the machine itself is just exhibiting extremely slow behaviour. I've never seen a machine do this. A lot of security updates had built up, so we decided to let Windows install them. When we looked through the history upon restarting, though, they had failed with error code 800706BA. I don't know if this could be related or not. Any help in this matter would be greatly appreciated. As mentioned in the title, we're running a Windows Server 2008 R2 machine. It's also running SQL Server and IIS. It has 16GB of RAM and a decent Quad Core processor. It's also been fine until now -- and we haven't changed a thing. Thanks for any help.

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• Why is dwm.exe using so much memory?

  - by Leonard Challis

  I've scoured the web, but I'm sick of reading "scan your computer for viruses" and "upgrade your RAM" on answers to similar questions to this. I understand that dwm.exe is for (simply put) caching bitmaps for things like Aero-peek and similar, but as far as I have read it shouldn't be using vast amounts of memory. My colleague and I both have 4GB of RAM, Core 2 Duo, blah, blah -- essentially they're pretty capable. His dwm.exe is running at around 30mb, mind is currently running at about half a gig, though it does fluctuate quite a lot. This is the same while running the exact same applications (currently Zend studio, FireFox (with firemin - low memory usage), Outlook). Every so often I will get a notification asking me if I want to switch to Aero Basic because it's using too much memory, and sometimes it will just switch itself to basic and let me know why. I know it's possible to stop it switching, but I want to know why it is using too much memory otherwise it's just papering over the cracks. One thing to add is this seems to have started after a robbery on Monday, where two of my monitors were stolen, and I had to temporarily use a couple of alternative monitors. I am now using brand new monitors but the problem is the same. All drivers installed and working seemingly fine. Any ideas why the usage is so high? We are using windows 7 64-bit Professional.

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• i7 Windows 7 laptop or Macbook Pro 15" (For making 3D model and Animation)

  - by sppdhs

  Hi everyone, I'm thinking of buying a new laptop as my current one will be 5 years old next year and it currently gives me a blue screen everytime I run a heavy software to make 3D models and animation. Question is: Should I buy Macbook Pro or a Windows 7 laptop? I tried to research and some say that Windows would be better, especially because you can buy a very high spec laptop with cheaper price. While some other say Macbook Pro is the better choice as it can run bootcamp with windows 7 100% performance on every software even though it's a mac. Is this true? Which one is actually better? Btw, the software that I usually use is 3Ds Max, Maya, and ZBrush. To note as well, I have never used a Mac before. I've checked around some stores and budget wise, I'll need around AU$3000+ to buy a Macbook pro, and AU$2000+ to buy a windows laptop. Quite a big difference in price range. Thanks in advance for your help.

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• Under what conditions will sendmail try to immediately resend a message instead of waiting for the standard requeue interval?

  - by Mike B

  CentOS 5.8 | Sendmail 8.14.4 I used to think that if SendMail experienced a temporary (400-class) error during delivery, it would place the message in a deferred queue (e.g. /var/spool/mqueue) and retry an hour later. For the most part, that appears to be the case. But every now and then, I'll notice log entries like this (email/domains renamed to protect the innocent :-) ) : Dec 5 01:43:03 foobox-out sendmail [11078]: qBE3l7js123022: to=<[email protected]>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=124588, relay=exbox.foo.com. [10.10.10.10], dsn=4.0.0, stat=Deferred: 421 4.3.2 The maximum number of concurrent connections has exceeded a limit, closing transmission channel Dec 5 01:53:34 foobox-out sendmail [12763]: qBE3l7js123022: to=<[email protected]>, delay=00:10:31, xdelay=00:00:00, mailer=relay, pri=214588, relay=exbox.foo.com., dsn=4.0.0, stat=Deferred: 452 4.3.1 Insufficient system resources Dec 5 02:53:35 foobox-out sendmail [23255]: qBE3l7js123022: to=<[email protected]>, delay=01:10:32, xdelay=00:00:01, mailer=relay, pri=304588, relay=exbox.foo.com. [10.10.10.10], dsn=2.0.0, stat=Sent (<[email protected]> Queued mail for delivery) Why did Sendmail try again just 10 minutes after the first attempt and then wait another hour before trying again? If this is expected behavior, what scenarios will cause this faster requeue interval to occur?

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• 3000 videos songs... some are loud in voice & some low.. I want to make them equal (equal in volume only)

  - by Mister.9

  I have thousands Video flv/avi files, which are all songs only. Some of them are high in volume and some are low. Every time the song ends I have to up or down the volume at once..to escape my ears ruined by headphones... and by woofers, save my life from my neighbor sleeping after hard-earning all the day long. :-( Any idea to make all files sound equal? Does such kind of application/software exist? Any converter that may convert all audio files into same volume? I know iTunes has sound-check option but can it convert? If I want to write CDs, does any burner have the feature like this, to burn in equal sound? If yes, suggest something for me... For, I am really really worried... It would be a great help..... Hoping your kind reply, Thanks in advance! (I am I am John.martin188@yahoo for having mails also in this regard)

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• Improve wireless performance

  - by djechelon

  Hello, I have a Trust Speedshare Turbo Pro router, which is running on channel 6. I found that the wireless signal (and network performance) dramatically drops from my PDA (I can barely attach to the network, even if I set the PDA's energy settings to maximum wireless performance) when I even exit my room, and I don't have shielded walls or something like that. I can't even stream a SD video from my desktop (connected via LAN) to my laptop using WiFi, while via LAN it works fine. I read that changing router's channel could improve performance due to interference reducing. I found that almost all wireless networks around here run on channels 6 and 11. I tried to go to my router's settings page to change channel, but I found that the combo box only allows me to select 6!! I'm not sure, but I may have been able in the past to change channel, though not to all of the available channels. A few minutes ago I tried a firmware upgrade, but it didn't solve my problem. My question is Is it possible that my router is someway locked to its channel? I bought it on my own, I didn't receive it from my ISP Apart from boosting the antenna power to the maximum (which, by the way, increases the EM radiation my and my family's bodies absorb 24/7 and is little more environment-unfriendly), do you have any tips on getting high quality transmission up to 5 metres from the antenna? Thank you

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• Apache2: Limit simultaneous requests & throttle bandwidth per IP/client?

  - by xentek

  I want to limit simultaneous requests & throttle bandwidth per IP/Client on a single apache vhost. In other words, I want to ensure that this site, which hosts large media files, doesn't get hammered by someone trying to download everything all at once (just happened the other night). I'd like to limit the outgoing transfer speed overall for this site, as well as limit the number of connections a single IP can make to the server to a sane default (i.e. within normal browser limits for multiple requests so page loads aren't effected too much). Bonus points if I can actually scope it to file types (i.e. leave web files alone, but apply these rules to just the media files). We're running Ubuntu 9.04 on all the servers, and have two apache/php servers being load balanced via Round Robin by a squid proxy server. MySQL is running on its own box as well. We've got plenty of bandwidth to give them, so I don't really want overall caps, but just want to throttle the amount of memory/CPU it takes to serve this site. There other sites on these servers that we don't want to apply these rules too, just want to keep this one from hogging all the resources. Let me know if you need more info! Thanks in advance for your suggestions!

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• No sound out of headphone port on laptop

  - by Thanatos

  I cannot get sound out of the headphone port on a laptop. Headphones are plugged in, and sound comes out of the internal speakers. Windows behaves normally (sound switches to headphones when headphones are inserted). It did work in Linux at one point, but something changed, we're just not sure what. Rebooting doesn't fix. This appears to occur whether or not PulseAudio is running. Things I've tried: Rebooting. No effect. Booting into Windows. It works properly, so probably not a hardware issue. All of alsamixer. My only controls are this: "Master" Volume bar & mutable, unmuted. Controls volume. "PCM" Volume bar only. 100%. "S/PDIF" Mutable only, currently muted, has no effect. "S/PDIF" Default PCM", Mutable only, currently unmuted, has no effect. Killing PulseAudio. No effect. (It also won't stay dead! Something appears to be restarting it, and I can't tell what, but it is annoying as fuck.) alsactl init 0, no effect. sudo rm -f /var/lib/alsa/asound.state, no effect. General system info: Ubuntu 10.04 LTS Toshiba Satellite T135D-S1324 lspci says I have: 00:14.2 Audio device: ATI Technologies Inc SBx00 Azalia (Intel HDA) 01:05.1 Audio device: ATI Technologies Inc RS780 Azalia controller Some edits: Yes, the headphones are in all the way. This works in Windows: You plug headphones in, the internal speakers stop making noise, and noise comes out the head phones. Windows says I only have two sound cards: the HDMI port (which I don't care about) and the "sound card", which it claims is a "Conexant Pebble High Definition SmartAudio" In Windows, both the internal speakers and the headphone jack show up as one soundcard, which in my experience, is typical. (This is a laptop)

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• What is the best private cloud storage setup

  - by vdrmrt

  I need to create a private cloud and I'm searching for the best setup. These are my 2 most important requirements 1. Disk and system redundant 2. Price / GB as low as possible The system is going to be used as backup setup which will receive data 24/7 over SFTP and rsync. High throughput is not that important. I'm planning to use glusterfs and consumer grade 4TB hard-drives. I have worked out 3 possible setups 3 servers with 11 4TB HDD Setup up a replica 3 glusterfs and setup each hard drive as a separate ext4 brick. Total capacity: 44TB HDD / TB ratio of 0.75 (33HDD / 44TB) 2 servers with 11 4TB HDD The 11 hard-drives are combined in a RAIDZ3 ZFS storage pool. With a replica 2 gluster setup. Total capacity: 32TB (+ zfs compression) HDD / TB ratio of 0.68 (22HDD / 32TB) 3 servers with 11 4TB consumer hard-drives Setup up a replica 3 glusterfs and setup each hard-drive as a separate zfs storage pool and export each pool as a brick. Total capacity: 32TB (+ zfs compression) HDD / TB ratio of 0.68 (22HDD / 32TB) (Cheapest) My remarks and concerns: If a hard drive fails which setup will recover the quickest? In my opinion setup 1 and 3 because there only the contents of 1 hard-drive needs to be copied over the network. Instead of setup 2 were the hard-drive needs te be reconstructed by reading the parity of all the other harddrives in the system. Will a zfs pool on 1 harddrive give me extra protection against for example bit rot? With setup 1 and 3 I can loose 2 systems and still be up and running with setup 2 I can only loose 1 system. When I use ZFS I can enable compression which will give me some extra storage.

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• Performance data collection for short-running, ephemeral servers

  - by ErikA

  We're building a medical image processing software stack, currently hosted on various AWS resources. As part of this application, we have a handful of long-running servers (database, load balancers, web application, etc.). Collecting performance data on those servers is quite simple - my go-to- recipe of Nagios (for monitoring/notifications) and Munin (for collection of performance data and displaying trends) will work just fine. However - as part of this application, we are constantly starting up and terminating compute instances on EC2. In typical usage, these compute instances start up, configure themselves, receive a job from a message queue, and then get to work processing that job, which takes anywhere from 15 minutes to over 8 hours. After job completion, these instances get terminated, never to be heard from again. What is a decent strategy for collecting performance data on these short-lived instances? I don't necessarily need monitoring on them - if they fail for whatever reason, our application will detect this and handle re-starting the job on another instance or raising the flag so an administrator can take a look at things. However, it still would be useful to collect information like CPU (user, idle, iowait, etc.), memory usage, network traffic, disk read/write data, etc. In our internal database, we track the instance ID of the machine that runs each job, and it would be quite helpful to be able to look up performance data for a specific instance ID for troubleshooting and profiling. Munin doesn't seem like a great candidate, as it requires maintaining a list of munin nodes in a text file - far from ideal for an environment with a high amount of churn, and for the short amount of time each node will be running, I'd rather keep the full-resolution data indefinitely than have RRD water down the data over time. In the end, my guess is that this will require a monitoring engine that: uses a database (MySQL, SQLite, etc.) for configuration and data storage exposes an API for adding/removing hosts and services Are there other things I should be thinking about when evaluating options? Perhaps I'm over-thinking this, though, and just ought to run sar at 1-minute intervals on these short-lived instances and collect the sar db files prior to termination.

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• What does "incoming" and "outgoing" traffic mean?

  - by mgibsonbr

  I've seen many resources explaining how to set up a server's firewall to allow incoming and outgoing traffic on HTTP standard ports (80 and 443), but I can't figure out why I would need either of them. Do I need to unblock both for a "regular" web site to work? For file uploads to work? Are there situations where it would be advisable to unblock one and leave the other blocked? Sorry if that's a basic question, but I couldn't find it explained anywhere (also I'm not a native english speaker). I know in a "regular" web site the client is always the one who initiates a request, so I'm assuming a web server must accept incoming traffic on those ports, and my common sense tells me the server is allowed to send a response without unblocking anything else (otherwise it wouldn't make sense to have two types of rules). Is that correct? But what is an outgoing web (service) traffic, and what would be its use? AFAIK if the server wanted to initiate a connection with another machine, the specific port that matters is the one in the other end (i.e. the destination port would be 80), on its end any free port could be used (the source port would be random). I can open HTTP requests from my server (using wget for instance) without unblocking anything. So I'm assuming my concepts of "incoming" and "outgoing" are wrong somehow.

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• Video card not detected in POST on initial boot.

  - by Jeff M

  I have a minor problem with my desktop computer after cleaning it out for dust. When I first boot up the computer, the video card does not get detected so I can't see anything. In POST, I'm getting the "can't detect video card" beeps. The boot sequence continues normally, just without video. However, if I restart it (using the restart button) anytime after POST, it would boot up normally. I have no reason to think that the motherboard, video card or PSU got damaged in the process. It was working fine before, works fine after resetting. Took all the necessary precautions while cleaning. On the initial boot, I can hear the video card's fan power up but immediately power down and try again one more time only to fail. After the beep, resetting gets everything running and sounding normally. I've reseated the card a couple of times and reset the BIOS but doesn't seem to help. I'm hoping I won't have to take it out and remove and reinstall everything again. Does anyone recognize these symptoms to know exactly what the problem is? My guess is that the video card isn't getting enough juice initially to be running stable to be detected. I just don't know what I did (or didn't do) to get it to be in this state. It's not a high priority thing for me at the moment, just means I have to always reset it after initially turning it on but will eventually remove everything and reinstall if it comes to that. I don't think the specs are relevant here but just in case, here's the relevant stuff: Motherboard: Gigabyte P35-DS3P Video: EVGA GeForce 8600 GTS PSU: Antec True Power Trio 650W Built ~2 years ago, still running well

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• Router vs switch in a LAN [closed]

  - by servernewbie

  If I have a LAN and and connect it with a switch, I understand it uses a CAM table to route packets in layer 2 (by saving mac to port relations). So far all good. However, when using a router for a LAN (ONLY for a LAN, not to connect it to "the outside" WAN/internet/etc) I get a bit confused as to how it internally processes packets. I would first split this into two router scenarios: Router with buit-in switch In this scenario, I would expect that it will act exactly as a switch with a CAM table internally. This would probably benefit a bit in speed (guessing here?) compared to the next option. Router without built-in switch Here is where I get confused. If hostA wants to send a packet to hostB, it will ARP to find hostB's MAC address and send it there. Now, if we had a switch (above scenario) this would be easy. But how does it work now in a router WITHOUT a switch? If I would guess, hostA would send an Ethernet frame with hostB's MAC address to the line. The router would fetch the packet (even though the router has another MAC address, it would still fetch this packet even if it only contains hostB's MAC address). It would strip the Ethernet frame header and check the IP, and then check its own internal ARP table again for the MAC address. Now, this would seem like a waste of resources compared to a router with a built-in switch. But maybe it does not work like that at all. Does it also contain a CAM table? If that would be true, what would then the difference between these two routers really be?

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• Intel Ethernet Bottlenecking Internet?

  - by Donald Darma

  I'm having trouble with my internet speeds. So I just recent build a pc and everything is fine. I installed the Intel drivers and connected to the internet. It connects but I'm only half the speed I should be getting. My normal speed is 20mbps but speedtest.net is only showing 10. It can't be my ISP (which is TWC if anyone is asking) because my other devices like my laptop and my smartphone are showing 20 down. Heres my system: CPU: i5 4430 HSF: Stock cooler Mobo: Gigabyte Z87MX-D3H GPU: x2 MSI R7950-3GD5/OC BE RAM: Crucial Ballistix Tactical Tracer 8GB dual channel PSU: Silencer High Performance Power Supply 750 Watt 80+ (It's a subdivision of OCZ) HDD: Seagate Barracuda 7200RPM 3TB SSD: Samsung 840 Evo 120 GB Case: Corsair Obsidian 350D Edit: I am using the stock adapter that is on the motherboard. I know for a fact that the cable is good because I used it on my laptop and it ran fine. Its a CAT5E cable. I also ran IPERF and its giving me the same results, 10 mbps.

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• Things to check for an internet-facing email server.

  - by Shtééf

  I'm faced with the task of setting up a public-internet-facing email server, that will be relaying mail for all of our other servers in the network. While the software in itself is set up in few keystrokes, what little experience I have with managing an email server has thought me that there are tons of awkward filtering techniques employed by other email systems. Systems that my own server will inevitably interact with a some point. Hence, my questions: What things should be kept in mind and double checked when setting up an email server? What resources are available for checking if my email server is set-up correctly? I'm specifically NOT looking for instructions for any given mail server, such as Exchange or Postfix. But it's okay to say: “you should have X and Y in your set-up, because when talking to server software Z, it typically tries to weed out open relays by checking for these.” Some things I've discovered myself: Make sure forward and reverse DNS are set up. Mail servers tend to do a reverse lookup for the peer IP-address when receiving. Matching a reverse look up with a follow-up forward lookup is probably employed to weed out open relays run through malware on home networks. Make sure the user in the From-address exists. The From-address is easily spoofed. A receiving mail server may try to contact the mail server in the From-domain, and see if the From-user actually exists.

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• Best way to build / implement a corporate developer Linux distro with multiple kernels?

  - by Garen

  At work we have Linux users who understandably prefer using Ubuntu. Problem is, we also have developer tools that only work with 'officially' supported Linux distributions that use much older 2.6.18 based kernels. (And even if they worked with newer ones, the vendors could always say they won't "support" the software unless it's on one of their 'officially' supported platforms.) We could of course just tell them to use CentOS or something else 2.6.18-based, and I'm sure their response would be something like: "you can take Ubuntu from our cold, dead hands." :) Which brings to me some questions--is there any good/easy/recommended way to run something like Ubuntu as a host VM and Centos 5.x as a guest OS (with which system--Xen,KVM,VMWare, ...?), and then roll that into our own custom internal distribution that could be easily installed? KVM looks like a good high-performance option just recently included in RHEL 5.4, but if hardware support for virtualization like Intel-VT or AMD-V is necessary, then I'd guess only those folks with fairly new PCs will be able to do it. Would be very interested to hear how anyone else has addressed this kind issue. EDIT: The target audience / users of this kind of system would be developers, each one needs to run locally licensed commercial software, so building out some separate beefy central machines isn't an option unfortunately due to license restrictions. Even if that weren't the case, a couple developers could quickly eat up the resources with parallel builds. :) Ideally, I was hoping there was some step-by-step guide out there to build your own pre-built distribution that had e.g. CentOS 5.x and Ubuntu Desktop as a guest.

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• Log shipping on select tables.

  - by Scott Chamberlain

  I know I am most likely using incorrect terminology so please correct me if I use the wrong terms so I can search better. We have a very large database at a client's site and we would like to have up to date copies of some of the tables sent across the internet to our servers at our office. We would like to only copy a few of the tables because the bandwidth requirement to do log shipping of the entire database (our current solution) is too high. Also replication directly to our servers is out of the question as our servers are not accessible from the internet and management does not want to do replication (more on that later). One possible Idea we had is to do some form of replication on the tables we need to another database on the same server and do log shipping of that second smaller database but management is concerned that the clients have broken replication (it was between two servers on their internal network however) on us in the past and would like to stay away from it if possible. Any recommendations would be greatly appreciated. If using some form of replication is the only solution, I am not against replication, I just need compelling arguments to convince management to do it. This is to be set up on multiple sites that are running either Sql2005 or Sql2008 we will have both versions on our end to restore the data to so that is not a issue. Thank you.

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