Any suggestions for a good homebrew rig to run a VM on?

September 4, 2006 5:10 PM

I'm looking to build a Virtual Machine friendly PC box. I'm hoping to spend no more then $600 on it to start (that will not include a moniter; I don't need one), but the key is to have it be quite expandable in the future (say 1 to 1.5 years). I don't need a lot of starting RAM, just enough to run one or two low demand VMs (one with XP on it). Any good suggestions for what I should look to buy (full specs please)? I assume I should be looking into the newer chips, right? Thank you!
posted by TrueVox to Computers & Internet (7 answers total)

You say you don't need RAM, but you ramble on about running VMs ... you do realise that VMs need plenty of memory, or your paging will be a dog, don't you?
Sorry, I don't have suggestions as to what to get, except don't skimp on the RAM if you actually plan to run VMs.
That will be 2 cents please.
posted by anadem at 6:11 PM on September 4, 2006

Virtualization is a tricky thing to benchmark, hence a tricky thing to set optimal specs around. It's highly variable, depending on your specific applications. Which VM software will you be using? VMWare workstation running atop a host OS, or something like ESX running on bare metal with XP guest OSes?

I'm guessing (based on your price range) you're going with VMWare Workstation or similar, atop a WinXP or RHEL install. If you could provide more detail on what it is you'd like to accomplish, I could be more specific and helpful.

Here are a few considerations...VMWare has been known to have issues (for which they've released patches) around multi-core/multi-CPU Intel Xeons. In some cases you may see a performance increase going with AMD Opteron, or at least disabling hyperthreading on the Intel CPUs. (This has to do with inconsistent scheduling of threads in multithreaded applications, NUMA scheduling. Long story. Depends on version, patch, architecture, etc.)

In my experience, if you're running VMs on top of a host OS, allow the standard amount of RAM for the underlying OS (say, 512MB - 1GB) , plus at least 1GB of RAM (actually 1024MB) to allocate to two VMs (minimum 512 each). You can scale beyond 2GB down the road. The extra RAM would go towards either granting more memory to a specific VM (making sure in advance that it's not a futile effort due to memory addressing limitations of the apps you're running in that VM) or towards supporting additional VMs running concurrently (different apps).

Don't skimp on the hard drive. Storage is cheap -- I don't know what your storage requirements/demands will be on these VMs, but suffice to say it's a few hours of downtime to resize a VM's virtual disk if your needs outgrow the amount of space you allocated to begin with. (And, at least AFAIK, you'll have to lose all your snapshots to do it.) So don't skimp on disk space -- go with a larger drive than you think you'll need. If you're guessing 120GB...buy a 200 instead. What's an extra 30 bucks?

The nice thing about VM appliances are that you can easily migrate them to upgraded hardware if/when you outgrow this rig. Copy the whole VM to a new machine and fire it up, and it's good to go. By the time you outgrow the rig, a lite version ESX with VMotion will probably be free and you can just do teaming. (Fingers crossed on that one. ;-)
posted by edverb at 7:13 PM on September 4, 2006

Well, XP isn't what I'd call a "low demand" anything, RAM-wise! I mean, you need at least ~384MB to run XP comfortably (personal experience). A gig RAM would let you run a host Linux system with Xen (doesn't need much, maybe 98-128MB), a WinXP VM with 512MB, and then you've got ~460MB left to allocate to a few more Linux VMs with varying amounts of RAM. Note that this is all assuming you are doing this to goof around and not to run some sort of business!

If I was to make a box that I wanted to run any sort of virtualization setup on that included XP, I'd definitely get some newerish processor that utilizes the new VT technology (I can't tell you which ones do, I believe the Intel Core (Duo) chips have it) which is required to run Windows under Xen. See this Wikipedia article for more about VT and other virtualization stuff.

Finally, is this for JUST virtual machine tinkering or would you be gaming on it as well? A decent video card is going to add at least $150-250 to your total costs, if not more.

So, let's see, some ruminations and suggestions, focusing on Intel only because it would take twice as much time to cover AMD as well (N.B.: I use an AMD64 in my beloved, 2-year-old gaming rig), with links to NewEgg, and being biased towards items with many, 5-egg reviews:

• Processor: Like I said, you should probably get one with VT, at whatever clockspeed gets you a good price right now, as clockspeed is not as important as the other aspects of the system.
  • Intel Pentium D 930 - $165 - Decent clockspeed, one of the few processors NewEgg seems to offer with VT support.



• Motherboard: You say you want it expandable, but unless your uses include gaming (on a VM, unlikely) I assume you just mean adding components, not upgrading existing ones. So just about any motherboard should do, considering that you will always have PCI slots and you can use those to add extra motherboard controllers and etc. Therefore, all that really matters is whether it's compatible with the processor you choose.
  • Intel 945G - $97 - 4 each of SATA controllers, PCI slots and RAM slots means plenty of expandability! /salespitch



• RAM: Mostly decided by what motherboard you go with. These days DDR2 seems to be the de facto standard. The motherboard above supports dual channel RAM but I've never actually used it so I am blithely assuming one does not need to use paired RAM with such a system.
  • Mushkin 1GB stick of DDR2 667MHz - $100 - This leaves you with 3 empty slots of RAM to fill it up to the motherboard's max of 4GB.



• Secondary storage:
  • Seagate Barracuda SATA 80GB - $49 - 80GB of space should be plenty, but then again I am the last person on the Internet who does not download ungodly amounts of video files.



• Other components: In here goes an optical drive (so you can install the various OSs onto your host and virtual systems), video, LAN, case, and anything else I haven't covered. The motherboard already has onboard video and LAN, which should be quite decent, and a decent DVD-ROM should cost you no more than $20-25, leaving you with the case (which can range quite a lot depending on quality and number of bays).
  


So, sans the "other components" above, this system would run you ~$405; with a $25 DVD-ROM and a $100 case you're up to $530, leaving you with $70 to spend on hookers and blow, or whatever :)

posted by cyrusdogstar at 8:05 PM on September 4, 2006

Ah, fucksticks, it added a ton of extra blank space :( Sorry about that, should have previewed more thoroughly.
posted by cyrusdogstar at 8:06 PM on September 4, 2006

I've found that RAM is always the first limiting factor as opposed to CPU. Think again about your RAM usage. Let's assume your using Windows XP Pro for your "Host" operating system. You'll want at least 384MB of RAM for it to use (not including your VMs). Then you open an XP VM. You'll want it to have at least 384MB of ram for it to use . Say you're running a Linux server on the second VM, running LAMP You'll want 512MB there. You're at 1.25GB.

If you're spending $600 sans monitor, get a big hard drive (or two. Backups are good. Losing 3 systems in a single HDD crash would suck) and a boatload of RAM (>=2GB).

Or, what edverb said.
posted by jeversol at 8:09 PM on September 4, 2006

Nope, I'll be jumping on the ram hard, but I only have limited means (read: Fiance and a kid thus can't spend too much at once but I can sometimes smuggle money out). However, this is not for a business, just for personal use. I want to use it for learning (setting up a small, VERY low load webserver on a DMZ VM), and for just running some different, cutting edge applications that I'm testing (The OFF System for one, if anyone cares). Also, eventully, *maybe* to run a version of Windows Media Center Edition (maybe, depending on load, reqirements, etc.). I'm just sick of losing my setup when I have to reformat my main server for various reasons, and at this point I'm not yet brave enough to go with a Linuxy variant on it (though I'm running Dapper on laptop that I'm currently typing from).

By the way, thank you all for the insightful answers. I'm sorry if I wasn't as clear as I should have been, but you all still have done admireably guessing at what holes I left out.
posted by TrueVox at 5:15 AM on September 5, 2006

Oh, and by the way, Cyrusdogstar, these hookers and blow - Can I get them with USB support? :)
posted by TrueVox at 5:16 AM on September 5, 2006