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• My PC is powercycling, what's going wrong?

  - by Renai

  So here is my sorry story of woe. My PC has been functioning normally for some time. Last week I bought a cheapish powered USB hub and plugged it into my home PC, which runs Windows 7. This weekend I plugged that hub into my home PC. At some stage I hibernated the PC. Then later on I plugged my Kobo eReader into the hub to charge. Later on I started the PC up. Only thing is, it now won’t start up. It just powercycles on for a second and a half with the fans at full, then powercycles off. Then back on for two seconds, then back off. There’s no display at all and it won’t get to the BIOS screen. It looks like anything USB is not functioning — the keyboard and mouse are not lighting up etc. I’ve taken out the BIOS battery and reseated the RAM, reseated the graphics card and so on, but my suspicion is that I have blown the USB section of the motherboard somehow. Suggestions? All else failing, where is the best place to take this machine in Sydney to get evaluated? It’s a fairly powerful beast, all up has cost me about $2500 over the years, including upgrades and a recent new graphics card, so can’t just start from scratch.

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• Is there a way to run CUDA applications with the CUDA device being a secondary adapter?

  - by Slartibartfast

  I've been trying to run a CUDA program on a remote computer which has Windows 7 installed. The GPU is GeForce GTX 480. One of the problems I've been facing is that, the computer has two adapters, 1) Standard VGA Adapter 2) NVIDIA GeForce GTX 480 Even though this shows in the device manager. The desktop uses the standard VGA Adapter. I'm assuming this is because the Standard VGA is the primary adapter. Also the device manager shows that the monitor is connected to the standard VGA Adapter. In this scenario if i try to run any CUDA application it fails to recognise a CUDA capable device. Is it necessary for the NVIDIA adapter to be the primary one? Or is there any way to use CUDA when the graphics card is a secondary adapter. I've seen a few posts in the NVIDIA forums on this before, one suggests using another low cost NVIDIA card as the primary adapter, but that is currently not an option. I couldn't find any other solutions. Thanks I tried running the deviceQuery test from the NVIDIA GPU Computing Samples. This was the result i obtained CUDA Device Query (Runtime API) version (CUDART static linking) cudaGetDeviceCount FAILED CUDA Driver and Runtime version may be mismatched FAILED The driver version I'm using is 263.06. The CUDA version is 3.2 I ran the same test on my desktop which also has windows 7 and a GeForce GTX 465. The CUDA toolkit version is 3.2. The driver version was the same and the test passed, although it failed with an older driver.

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• How is made sure magnetic or electric fields from devices like transformers or fans close nearby do

  - by matnagel

  Fans and transformers which are inside the server case create magnetic and electric fields. Electric fields can be easily shielded, but what about magnetic fields, they can only be shielded with high cost materials like mu metal http://en.wikipedia.org/wiki/Mu-metal If a hard drive is installed too close to an intense transformer field, how is the magnetically stored information on the ferromagnetic surfaces of the disk kept safe? Even if drives are shielded, where are the limits? Is there some technical investigation or recommendation from manufacturers about this? (I never heard about something and never had any problem but I am interested in some facts. This is much preferred over what you believe or a habit you developed. Please try to give some solid infromation.) I have built and repaired many servers and sometimes I did put the harddrive on top of the power supply. Edit: This question is not about frequencies that could affect the drive via the power or data connectors of the drive, those are electronically decoupled and that's another question. Edit 2: The wikipedia page states that the motor inside the drive is shielded with mu metal. It is obvious that manufactureres have to take care of this. This question is about such influences from outside the drive.

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• DNS failover in a two datacenter scenario

  - by wanson

  I'm trying to implement a low-cost solution for website high availability. I'm looking for the downsides of the following scenario: I have two servers with the same configuration, content, mysql replication (dual-master). They are in different datacenters - let's call them serverA and serverB. Users use serverA - serverB is more like a backup. Now, I want to use DNS failover, to switch users from serverA to serverB when serverA goes down. My idea is that I setup DNS servers (bind/powerdns) on serverA and serverB - let's call them ns1.website.com and ns2.website.com (assuming I own website.com). Then I configure my domain to use them as its nameservers. Both DNS servers will return serverA IP as my website's IP. If serverA goes down I can (either manually or automatically from serverB) change configuration of serverB's DNS, to return IP of serverB as website's IP. Of course the TTL will be low, as it's supposed to be in DNS failovers. I know that it may take some time to switch to serverB (DNS ttl, time to detect serverA failure, serverB DNS reconfiguration etc), and that some small part of users won't use serverB anyway. And I'm OK with that. But what are other downsides of such an approach? An alternative scenario is that ns1.website.com will return serverA IP as website's IP, and ns2.website.com will return serverB IP as website's IP. But AFAIK clients not always use primary nameserver and sometimes would use secondary one. So some small part of users would use serverB instead of serverA which is not quite what I'd like. Can you confirm that DNS clients behave like that and can you tell what percentage of clients would possibly use serverB instead of serverA (statistically)? This one also has the downside that when serverA goes back up, it will be automatically used as website's primary server, which is also a bad situation (cold cache, mysql replication could fail in the meantime etc). So I'm adding it only as a theoretical alternative. I was thinking about using some professional DNS failover companies but they charge for the number of DNS requests and the fees are very high (why?)

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• Server 2008R2 in Extra Small Windows Azure Instance?

  - by Shawn Eary

  Windows Azure hosting for an Extra Small (XS) Windows VM seems to come out to be about $10 a month right now. I think this XS instance gives you the equivalent of a 1 GHZ CPU with 768MB of RAM. I think the minimum requirements for Server 2008 is 1GHZ CPU with 512MB of RAM. Also, I think the minimum requirements for SQL Server Express is 1GHZ CPU with 256 MB of RAM and that the minimum requirements for Team Foundation Server Express 11 Beta is 2.2 GHZ CPU with 1 Gig of RAM (this 2.2 GHZ part could be a problem for my 1 GHZ XS VM...). Given the performance of the XS Azure instance, would I be able to install: a very basic MVC web site; a free instance of SQL Server Express; a free single user instance of Team Foundation Server Express 11 Beta and run the XS VM instance without serious crashing? I know there are other Shared WebHost providers that can provide these features for me, but those hosting providers have the following disadvantages: They sometimes cost a lot of money after all of the "addons" are in place They probably don't provide the level of security and employee integrity that Microsoft can provide They don't provide the total control that an Azure VM seems to provide

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• Install and enforce a scheduled task across a Windows domain

  - by Ricket

  We have a small domain of about 70 Windows computers (XP and 7). We want to schedule a command (an update mechanism) to run on all computers periodically, and we want the task to run regardless of the computer's connection to our network (i.e. the task should run even on a laptop that isn't connected to our VPN). We have a Microsoft System Center Essentials 2010 server so that might come in handy. The options I see are these: Do it completely manually. Install the scheduled task by hand or remotely using psexec (and the at command?) for each computer in our network. Enforce that newly imaged computers should have this task installed on them before deployed to the employee, or the task should be in the image. High initial cost (having to do this for each of 70 computers) but building it into the image might work... But there is some maintenance in making sure the task is added to everything. And I fear that a year or two down the road, we will have forgotten about it or gotten sloppy or had new IT employees who miss this step and some computers won't have the task. Having one of our servers run a script that loops through all computers and psexec's the command on each computer in the network -- it would only run on running, connected computers, so this solution wouldn't work. I suspect SCE could do something like this too, but again this is not a good solution. Neither of these are ideal, and I'm certain there is a better way to do it -- right? What is the best way to accomplish this task?

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• 10GE network: Is it still deadly expensive? Any options?

  - by BarsMonster

  Hi! I am building home cluster where I going to have about 16 nodes which can live with 1G ports, but I really want to have 10GE on file server & central node. It's all local, so no need for cabels longer than 3-5m. And ofcourse I want to spend as little money as possible (not going to spend more than whole cluster costs) :-) What are my options? 1) Legacy solution is to take some 24-48 port 1GE switch, and connect to file/central nodes via 4-8 aggregated links. This will work I guess, cost is very acceptable, but I am not sure if it's ok to use that much aggregated links. And ofcourse it would be hard to double bandwidth when needed... :-D 2) Switch with several 10GE uplink 'ports'. As far as I see, they all require modules which costs about 1000$, so I will need 4 10G modules, and 2 10GE cards... Smells like way more than 5000$+... 3) Connect file & central node via 2 10G cards directly, and put 4 quadport 1GE NICs on fileserver. I am saving on 2 10G modules and a switch, fileserver will have to do packet routing, but it's still gonna have alot of CPU's left :-) 4) Any other options? Infiniband? 5) Are MyriNet adaptors works fine? I guess there are no cheaper options? 6) Hmm... Scrap fileserver, put it all on central node and provide dedicated 1GE port for each of the nodes... This is sad...

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• Why do hosts prefer Linux to Windows Server?

  - by iconiK

  So far I see a HUGE majority of hosts provide only Linux shared hosting, providing Windows only to VPS (or even to only dedicated servers). Why is it so? While Windows is a lot more expensive than Linux (though it depends on a lot of factors, not just initial and support license cost), it also provides ASP.NET, IIS and of course, Microsoft SQL Server. I know in the past it might have been because of cPanel being Linux only but now they have a Windows version. But still, why is Linux predominantly used on shared hosting? PHP works on both systems. IIS can be (and probably is) faster. MySQL runs on both systems as well. cPanel has a Windows version. Python, Perl, Ruby, all run on Windows as well. You even have MS SQL Server Express, which I find more superior than MySQL in both speed and features. Access is there for low usage requirements, as is SQLite (which is so great for quick small stuff). And with PowerShell you have a good alternative to the Unix shell. EDIT: I am looking for common reasons, I realize each hosting company (and/or it's clients) may have different needs. This becomes very important when you get to VPS or Cloud which give you a full operating system to use.

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• Getting rid of your server in a small business environment

  - by andygeers

  In a small business environment, is it still necessary to have a central server? Speaking for my own company (a small charity with about 12 employees) we use our server (Windows Server 2003) for the following: Email via Microsoft Exchange Central storage Acting as a print server User authentication / Active Directory There are significant costs associated with running a server like this: Electricity, first for the server itself then for the air conditioning required (this thing pumps out a lot of heat) Noise (of which there is a lot) IT support bills (both Windows Server and Exchange are pretty complicated, and there are many ways they can go wrong) I've found ways to replace many of these functions with cheaper (better?) alternatives: Google Apps / GMail is a clear win for us: we have so many spam related problems it's not even funny, and Outlook is dog slow on our aging computers You can buy networked storage devices with built in print servers, such as the Netgear ReadyNAS™ RND4210 that would allow us to store/share all of our documents, and allow us to access printers over the network The only thing that I can't figure out how to do away with is the authentication side of things - it seems to me that if we got rid of our server, you'd essentially have a bunch of independent PCs that had no shared pool of user accounts / no central administrator. Is that right? Does that matter? Am I missing any other good reasons to keep a central server? Does anybody know of any good, cost-effective ways of achieving the same end but without the expensive central server?

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• What's needed in a complete ASP.NET environment?

  - by Christian W

  We have a ASP3.0 application with a few ASP.NET (2.0) dittys mixed in. (Our longtime goal is to migrate everything to ASP.NET but that's not important for this issue) Our current test/deploy workflow is like this: 1 Use notepad++ or VS2008 to fix a bug/feature (depending on what I have open) 2 Open my virtual test-server 3 Copy the fixed file over, either with explorer, or if I can be bothered to open it, WinMerge 4 Test that the fix works 5 Close the virtual test-server 6 Connect to our host with VPN 7 Use WinMerge to update the files necessary 8 Pray to higher powers that the production environment is not so different that something bombs. To make things worse, only I have access to my "test-server". So I'm the only one testing it. I really want to make this a bit more robust, I even have a subversion setup running. But I always forget to commit changes... And I don't even work in my checked out folder, but a copy of what is currently in production... Can someone recommend some good reading on deploying, testing, staging and stuff like that. I currently use VS2008 and want to use subversion or GIT (or any other free VCS). Since I'm the only developer, teamsystem is not really an option (cost-related). I have found myself developing an "improved" feature, only to find a bug in the same feature in the production system. And since my "improved" feature incorporated deleting some old functionality, I have to fix bugs directly in production... That's not a fun feeling... (I have inherited this system recently... So it's not directly my fault that it is like this ;) )

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• Can any iSCSI NAS appliance replicate / clone a LUN to an external drive?

  - by Boden

  I would like to backup using Windows Imaging to some kind of NAS appliance. I believe this will require the NAS to support iSCSI. I would then like the appliance to support the replication of the iSCSI LUN to an external eSATA or USB disk connected directly to the appliance. I've found plenty of NAS appliances that can do iSCSI and replicate to an external drive, but none that I've found thus far can do both at once. That is, the devices can do iSCSI, but then the replication feature doesn't work. The idea here is to backup to an appliance located in a secure office far away from the server room. Offsite backups to external hard drive could be managed from the appliance. The benefits of such a setup would be: 1) very unlikely that fire or random theft would affect both server-room backup and "remote" backup appliance 2) offsite backups could be managed by multiple trusted people without granting access to server room 3) Windows imaging provides poor man's deduplication, so each backup volume can contain a decent backup history. I understand why this would be a non-trivial thing to implement, but I'm wondering if such a thing exists? Preferably a tabletop, low to medium cost device. Alternative solutions welcome. NOTE: I'm backing up very few but very large files, so file replication is not a good option.

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• Supermicro IPMI on MBD-X8DAH+-F-O motherboard. Keyboard and mouse do not work after booting Windows Server 2008 R2

  - by LDelgado

  Hell Everyone, I built a server with the mentioned motherboard. I installed Windows Server 2008 R2 Enterprise on this server. IPMI is integrated on the motherboard with its own dedicated NIC. I've got that NIC configured with its own IP address. I can remote into it using IPMI, and I can remotely control the server settings before booting the OS ( BIOS, RAID configuration, etc). When the OS boots, I lose the mouse and keyboard. I cannot use the keyboard or mouse when installing the OS either. So the Keyboard and Mouse only work when no OS is loaded. Once the OS loads I lose it - that is my problem. I've been doing some research and trying a few things, but I have not been successful in fixing this issue. I may be wrong, but based on the things I've found online, it seems that the problem could be caused by the way the OS handles USB. The server is headless. There is no keyboard, mouse, or monitor plugged into it. When I boot up the OS and remote into it, I cannot see a mouse or keyboard listed in the Device Manager. Based on what I've read, it seems that the OS should detect a mouse and a keyboard when connecting remotely via IPMI. The following are the solutions I've tried. Nothing has worked so far: I've updated the firmware of the IPMI component to the latest firmware - 1.33. I made sure that the mouse mode was set to Absolute (Windows OS). I've loaded the factory defaults several times. I've enabled Port64h/60h Emulation under the USB settings in the BIOS. I've disabled USB legacy support in the BIOS. I made sure the firewall wasn't blocking IPMI (disabled the firewall). And that's about it. I've found threads in some forums from people having the same issue as me, but they were not running the same OS. They were either running Linux or FreeBSD. Most of them fixed their problem by selecting the right mouse mode (Linux in their case). There was one other that solved the problem by disabling USB Mass Storage mode. He stated "When I set it to disable USB Mass Storage when no image is loaded, the ukbd came alive, and I'm typing this on the IPMI Console. " source: http://freebsd.1045724.n5.nabble.com/IPMI-Console-No-luck-once-OS-is-booted-td3967868.html I suspect the solution described in the previous paragraph is somehow related to my problem. I've found several threads on the internet with issues describing the same problem, but none of them were with Windows Server 2008 R2. Again, I may be wrong, but it seems like that could be the issue. I just don't know how I go about applying a solution in Windows Server 2008 R2. In any case, I could use your expertise. Maybe I am missing something, or maybe I'm on the right track. Your help is much appreciated. Thank you in advance,

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• Setting up MySQL Linux slave with a Windows master

  - by philwilks

  I'm running a MySQL 5.0 database server on Windows Server 2008. The total size of the database is about 1Gb. I make daily backups, but I'd like to step up to having a slave server for extra protection. My thinking was that I wouldn't need the expense of a Windows machine to do this, and a Linux "cloud server" from RackSpace would do the job well for quite a low cost. However I have little experience with Linux, so I have a few questions... Does this sound like a good idea? Is there anything wrong with linking Windows and Linux MySQL servers? Does Linux have the equivalent of Remote Desktop Connection? If so can I use this from a Windows machine? Would a particular Linux distro be well suited to this task? RackSpace offer ArchLinux, CentOS, Debian, Fedora and Ubuntu. My immediate thinking is to go with Ubuntu as I've heard it's more friendly for people coming from a Windows background. Any comments you have would be very appreciated! Phil

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• Why do you use a 3PAR SAN? [closed]

  - by Starfish

  If you use a 3PAR SAN, I’d like to hear what you think about it, particularly compared to the HP EVA. What do you see as its advantages over other SANs like the EVA? What’s so special about the ASIC? We had HP quote us an EVA P6500 and 3PAR V400 with equivalent storage and the 3PAR was nearly twice the cost. My site has two EVA SANs with a combined capacity of ~80 TB. We want to replace the older and larger of the two. We’ve been looking at the EVA and the 3PAR to see which would be a better fit for us. I’m struggling to understand how the 3PAR differs from the EVA from a practical technical standpoint. When I read the sales literature and speak with the HP sales engineers, they spend a lot of time talking about how the 3PAR is better because of its ASIC. It’s ASIC this and ASIC that, but when I press them on how a 3PAR with thin provisioning is better than an EVA with thin provisioning, I can’t get a straight answer. Meanwhile, one of my colleagues, who has more say regarding which SAN we get, is enamored by the 3PAR, and he can’t explain clearly to me why he wants it over the EVA. Our needs are pretty simple. We have 10 servers running VMware and ~100 VMs. We use VMware’s thin provisioning currently, but we would like to start using thin provisioning on the new SAN. We don’t have a need for SSDs or migration between storage tiers. We plan on having FC or SAS drives for our most used data and SATA/FATA drives for the lesser used data which is how we have the EVAs configured. We also do not need any SAN-level snapshotting or replication.

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• Docking Station Sound Doesn't Work on Dell D830 with Windows 7

  - by cisellis

  I have a Dell Latitude D830 laptop that is running Windows 7 Enterprise x64. I connect to a docking station during the day with multiple monitors, a keyboard and a mouse. Everything runs with no problems including most of the docking station ports (usb, monitors, etc.) However, the sound port from the docking station does not work since the upgrade to Windows-7. Even with the laptop plugged in, the sound always comes out of the laptop, not the headphones plugged into the docking station. Here's what I've tried: I've seen other issues like via Google this that seem to be mostly unanswered. I found one or two that referenced using the Vista x64 drivers, especially the Nvidia drivers. I do not have an Nvidia chipset but I've reinstalled the sound drivers and that has not helped. I don't have a support contract and considering the cost is usually high to call Dell, that's not an option. Dell's forums are pretty much a wasteland and I've found no help there. Since this is a docking station I thought I might need to try the SATA or Intel chipset drivers from the dell site instead, however I'm not really sure and I need to work on this laptop in the meantime. I can't really afford the downtime to experiment with random drivers all day in case they turn out to be incompatible (Dell still hasn't added Windows 7 to their support site as far as I can tell). Does anyone have any other ideas? Has anyone had this issue and solved it? If so, how? Thanks in advance for your help.

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• Why does my PC successfully boot only when unplugged for more than a few minutes?

  - by philg

  I have an HP Pavilion Elite desktop computer, model HPE-490t. I like it because it didn’t cost too much, boots itself from an SSD, came with 16 GB of RAM, and has 6 CPU cores for editing video and camera RAW images. It has one behavioral quirk that I cannot explain, however. The recent power interruptions here in the Northeast got the machine into a state where it could not be restarted. It would power up for a second or two, shut down, and then power up again, never being able to get to the point of showing anything on the monitor. I unplugged it for about 10 seconds and plugged it back in. Same behavior (fails to boot). I unplugged it and walked away for an hour, then plugged it back in and it worked perfectly! I think something similar happened after installing a second hard disk drive into this machine. So the question is why does the computer behave differently depending on how long it has been unplugged? Where is energy stored that affects the machine’s ability to boot? Capacitors in the power supply? Battery on the motherboard (there is one for the clock, but that wouldn’t be exhausted by being unplugged for an hour, I don’t think)?

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• Why do manufacturers not show all hardware power usage?

  - by Drew

  I find it slightly more difficult to build a computer when I do not know how much power is needed for a component. When selecting a power supply for a computer, it is difficult to know how large of one to get. You don't want to go too large for cost reasons and circuit reasons, but you don't want to go too low and not be able to properly use every component. For instance, a graphics card might say "Minimum of a 500 Watt power supply. (Minimum recommended power supply with +12 Volt current rating of 30 Amps.)" But it really needs 360W (12V * 30A). So why don't they just say "Uses 360W max and xxxW peak"? Processors, I have noticed are good at reporting their power usage, but aside from processors and sometimes graphics cards, power usage is easily found. What is the power consumed by the Blu-ray / DVD drives? By the HDDs/SSDs? By the Mobo? etc. Why are these questions not easily answered when building a machine?

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• setup lowcost image storage server with 24x SSD array to get high IOPS?

  - by Nenad

  I want to build let's name it a lowcost Ra*san which would host for our social site the images (many millions) we have 5 sizes of every photo with 3 KB, 7 KB, 15 KB, 25 KB and 80 KB per Image. My idea is to build a Server with 24x consumer 240 GB SSD's in Raid 6 which will give me some 5 TB Disk space for the photo storage. To have HA I can add a 2nd one and use drdb. I'm looking to get above 150'000 IOPS (4K Random reads). As we mostly have read access only and rarely delete photos i think to go with consumer MLC SSD. I read many endurance reviews and don't see there a problem as long we don't rewrite the cells. What you think about my idea? - I'm not sure between Raid 6 or Raid 10 (more IOPS, cost SSD). - Is ext4 OK for the filesystem - Would you use 1 or 2 Raid controller, with Extender Backplane If anyone has realized something similar i would be happy to get Real World numbers. UPDATE I have buy 12 (plus some spare) OCZ Talos 480GB SAS SSD Drive's they will be placed in a 12-bay DAS and attached to a PERC H800 (1GB NV Cache, manufactured by LSI with fastpath) Controller, I plan to setup Raid 50 with ext4. If someone is wondering about some benchmarks let me know what you would like to see.

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• Windows VPN for remote site connection drawbacks

  - by Damo

  I'm looking for some thoughts on a particular way of setting up a estate of machines. We have a requirement to install machines into unmanned, remote locations. These machines will auto login and perform tasks controlled from a central server. In order to manage patching, AV, updates etc I want these machines to be joined to a dedicated domain for this estate. Some of the locations will only have 3G connectivity (via other hardware), others will be located on customer premises in internal networks. The central server (of ours) and the Domain Controller will be on a public WAN. I see two ways of facilitating this. Install a router at each location and have a site to site VPN between the remove device and the data centre where the servers are location Have the remote machine dial up and authenticate via a Windows VPN connection to the DC via RAS Option one is more costly to setup and has a higher operational cost. It also offers better diagnostics if the remote PC goes down. Option two works well but is solely dependent on the VPN connection been made before any communication can be made to the remote machine. In a simple test, I can got a Windows 7 machine to dial a VPN prior to authentication to a domain, then automatically login to the machine using domain credentials. If the VPN connection drops, it redials. I can also create a timed task to auto connect every hour in case of other issues. I'd like to know, why (if at all) is operating a remote network of devices which are located in various out of band locations in this way a bad idea? Consider 300-400 remote machines all at different sites. I'd rather have 400 VPN connections to a 2008 server than 400 routers, however I'd like to know other opinions on this.

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• Will wear induced by turning computers off in the evening be offset by energy savings?

  - by sharptooth

  I'm asking this here because this is primarily a huge office scenario and administrators will more likely have the answer I'm looking for. Employees' desktop computers can be either left turned on for the whole night or switched off in the evening and turned back on in the morning. The latter will surely save energy. In the same time turning on and off is very harmful for the equipment - hardware often breaks specifically when turned on. Both energy and hardware replacements cost money. With energy it's quite obvious - you pay every month according to what your power meter shows. With hardware replacements it's worse - you need qualified stuff to quickly diagnose the problems and once something breaks the affected employee will have to wait for some time while his computer is fixed/replaced and the data is recovered. So the company has to choose between saving money on energy and saving money on computer maintaince and lost hours. Such decisions must be well though. Is there any detailed study of how turning computers off each evening affects their lifetime?

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• Block SMTP session with sender domain which doesn't itself accept SMTP connection.

  - by bignose

  I'm administrating a mail service for a small business. Their mail host's internet connection is an ADSL service with a permanent IP address. Unfortunately, many misconfigured mail systems will happily deliver to this host, but, when the host attempts to send mail back (e.g. a bounce notice, or a normal response from someone), the declared sender's domain has an MX which refuses to receive connections from this host. That misconfiguration makes their system a one-way mail sender, which is a problem. How can I configure Postfix on this customer's mail host to refuse SMTP sessions that declare a sender domain which itself refuses SMTP from this host? That is, if the SMTP client declares a domain that we can't make SMTP connections back to, then there's not much point accepting the incoming connection in the first place. Note that I'm not, as some commenters have assumed, talking about checking whether the SMTP client will receive messages. The check I want is whether the declared sender's domain (regardless of who the current SMTP client is) will accept SMTP connections from here. In other words: when we get around to sending a message back, we'll need the sender's domain to accept SMTP connections; I want to do that check before accepting the incoming session. I'm imagining a late check (after the low-cost checks to winnow most of the rubbish connections) that keeps the client on the other end while it attempts an SMTP client connection back to the declared domain of the sender. If that connection is rejected, the incoming one is also rejected. I'm also open to other suggestions for how this problem might be addressed (short of not using this mail host at all, which isn't an option).

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• how to set up dual wireless routers (G and N) with single broadband connection

  - by user15973

  A local cafe has an 802.11g wireless router attached to either an 8- or 12Mbs broadband connection. Although many customers still have -g devices, an increasing number are showing up with 802.11n devices (e.g. Mac laptops, iPads). The cafe owner is content with his router's area coverage, but he would like for his customers to be able to take advantage of the higher -n download speeds. He could simply replace the -g router with a -n router, but reportedly -n routers slow down considerably when servicing both -g and -n connections. Another option would be to buy the -n router, run an Ethernet cable between the two routers, and (of course) hook up the broadband connection to one of the two routers. Still another option would be to attach an ordinary, wired switch to the broadband connection and then attach both routers to the switch. Aside from the cost issue, what are the tradeoffs of those approaches? Which would you recommend, and why? Is there a better option than the ones I mentioned? Thank you in advance for your advice.

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• What to look for in a switch with LAN/WAN verses an iSCSI SAN?

  - by Luke

  I'm setting up a VMWare ESXi 5 environment with 3 server nodes. Dell recommended 2x Force10 S60 switches shared (iSCSI SAN, LAN/WAN). The S60 switches are extremely powerful. They have 1.25 GB of buffer cache, < 9us latency. But they are very expensive (online price ~$15k per switch, actual quote a little less). I've been told that "by the book" you should at least have 2 internal switches for SAN, and 2 switches for LAN/WAN (each with a redundant). I know some of the pros and cons of each approach. What I'm wondering is, would it be more cost effective to disjoin the SAN from LAN with less expensive switches? The answer to this question highlights what I should be looking for in a switch for the SAN. What should I be looking for in a LAN/WAN switch, in comparison to the SAN? With the above linked question for the SAN: How is buffer latency measured? When you see 36 MB of buffer cache, is that shared or per port? So 36 MB would be 768kb or 36MB per port? With 3 to 6 servers how much buffer cache do you really need? What else should I be looking at? Our application will be heavily using HTML5 websockets (high number of persistent connections). The amount of data being sent is small; Data sent between client <- server isn't broadcasted (not a chat/IM service). We will be doing some database reporting too (csv export, sums, some joins). We are a small business and on a budget. We'd probably only be able to spend no more than $20k on switches total (2 or 4).

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• How far should we take the N+N redundancy craziness ?

  - by Brann

  The industry standard when it comes from redundancy is quite high, to say the least. To illustrate my point, here is my current setup (I'm running a financial service). Each server has a RAID array in case something goes wrong on one hard drive .... and in case something goes wrong on the server, it's mirrored by another spare identical server ... and both server cannot go down at the same time, because I've got redundant power, and redundant network connectivity, etc ... and my hosting center itself has dual electricity connections to two different energy providers, and redundant network connectivity, and redundant toilets in case the two security guards (sorry, four) needs to use it at the same time ... and in case something goes wrong anyway (a nuclear nuke? can't think of anything else), I've got another identical hosting facility in another country with the exact same setup. Cost of reputational damage if down = very high Probability of a hardware failure with my setup : <<1% Probability of a hardware failure with a less paranoiac setup : <<1% ASWELL Probability of a software failure in our application code : 1% (if your software is never down because of bugs, then I suggest you doublecheck your reporting/monitoring system is not down. Even SQLServer - which is arguably developed and tested by clever people with a strong methodology - is sometimes down) In other words, I feel like I could host a cheap laptop in my mother's flat, and the human/software problems would still be my higher risk. Of course, there are other things to take into consideration such as : scalability data security the clients expectations that you meet the industry standard But still, hosting two servers in two different data centers (without extra spare servers, nor doubled network equipment apart from the one provided by my hosting facility) would provide me with the scalability and the physical security I need. I feel like we're reaching a point where redundancy is just a communcation tool. Honestly, what's the difference between a 99.999% uptime and a 99.9999% uptime when you know you'll be down 1% of the time because of software bugs ? How far do you push your redundancy crazyness ?

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• Can a website company that builds 4-5 websites a year afford dedicated hosting?

  - by Petras

  We manage about 30 websites that use shared ASP.NET SQL Server web hosting. These are typical small/medium business websites and they perform fine in this environment. Recently I was looking at VPS hosting in this thread http://serverfault.com/questions/128329/how-do-you-host-multiple-public-facing-websites-on-a-vps After contacting a provider in one of the replies I was told that VPS hosting is not recommended for 30 sites, even if they are small. The resource requirements might be too great even for VPS. So I should turn to dedicated hosting. The lowest cost dedicated hosting is $219 per month (see http://www.serverintellect.com/dedicated/pentiumdservers.aspx). But this is only for a single processor which seems too light for a machine running both IIS and SQL. In our office all the developers work on quad cores so I assume I’d really need the Quad Processor. However, this starts at $599 monthly. Now, I won’t be able to transfer all of our 30 sites to this machine. I’d only be able to transfer say 5 or 6. However, moving forward, I’d be able to host all future sites on this machine. This amounts to 4-5 per year. Let’s look at the economics. Shared hosting costs are typically $16.95 monthly (see http://www.crystaltech.com/dotnet.aspx). So here’s the dilemma First months costs: $599 First month revenue: 6x$16.95 = $101.7 Loss in first month: $497.3 First year costs: $599x12=$7188 First month revenue: 6x$16.95x12 + 5x$16.95x6(averaged) = $1728.9 Loss in first year: $5459.1 Clearly it is going to take years for this server to pay for itself. It just doesn’t seem economical! Am I missing something here, or is dedicated not the way to go with the amount of sites we build?

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