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I would like to know how these 2 scenarios would impact each virtual machine on the performance side. I understand the risk of loosing a disk, I can deal with a downtime of a couple of hours.

I need to have 6 Hyper-V VM on one machine. 2 moderate web servers, 2 moderate database servers, 1 backup server, 1 test server that will compile stuff. And I need it cheap: let's say I use a big bunch of 7K SATA disks (up to 12).

Question: performance wise, am I better with one big RAID 10 volume or with each disk being separated? If I'm doing one big raid volume, could one VM do too much HD activity and impact the others? Is there the same problem if I use one or two HD per VM?

Carl

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The part that worries me is the '2 moderate database servers'. In my experience, there's no such thing, and this is something that just won't virtualize as well. –  Joel Coel Feb 17 '11 at 17:28
    
Disagree. I've got dozens of database servers that are moderate. They virtualize just fine, as long as you follow the recommended procedures. Check out Virtualizing Microsoft Tier 1 Applications, published by Sybex. It'll point you in the right direction with regards to SQL virtualization. That said, I think others are on the right track. A single RAID 10 is the way to go. –  B. Riley Feb 17 '11 at 21:41
    
B. Riley: This seems to go contrary to what Microsoft is suggesting: microsoft.com/whdc/system/sysperf/Perf_tun_srv-R2.mspx "Placing VMs with highly disk-intensive workloads on different physical disks will likely improve overall performance. For example, if four VMs share a single disk and actively use it, each VM can yield only 25 percent of the bandwidth of that disk." –  Malartre Feb 21 '11 at 16:58
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3 Answers

RAID 10 is extremely high performance with large numbers of drives, so I would recommend that path. You're more likely to run into a controller bandwidth bottleneck before you hit the individual drives' performance peak. In addition, the configuration overhead of dealing with multiple volumes will take a lot of time and effort and be prone to errors.

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Dave, to me it look like this: 1xRaid10 with 10 HD with 5VM will try to separate the bandwith equaly between the 5 VMs and will allow burst. 5xRaid1 with 2 HD will absolutely separate the bandwith equaly without allowing burst, but is less prone to bandwith problem. Do you see other properties? –  Malartre Feb 21 '11 at 17:03
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Do it with one RAID 10 volume - end of story.

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This answer would be more useful if it provided some justification for the choice. –  daveadams Feb 17 '11 at 16:21
    
Doesn't mean it's a wrong answer though and your own answer is hardly encyclopaedic. –  Chopper3 Feb 17 '11 at 16:41
    
I don't think an answer is helpful if it doesn't give the questioner any indication of the reasoning. Are you recommending one volume for performance sake? For ease of management? The correctness of your answer depends on the context. For this questioner, your answer is fine. For the next person who finds this post via Google, maybe your answer would not work in their context, and without any explanation, they won't have any means to judge. –  daveadams Feb 18 '11 at 13:57
    
well you're going to be busy if you start looking around, not everyone, especially those who already put 4-8 hours per week, for free, into moderating always has time to provide a detailed response when a question is as black and white as this. Go on, go knock yourself out, you can probably find enough like this to use all your votes as downvotes every single day. –  Chopper3 Feb 18 '11 at 15:15
    
This seems to go contrary to what Microsoft is suggesting: microsoft.com/whdc/system/sysperf/Perf_tun_srv-R2.mspx "Placing VMs with highly disk-intensive workloads on different physical disks will likely improve overall performance. For example, if four VMs share a single disk and actively use it, each VM can yield only 25 percent of the bandwidth of that disk. " –  Malartre Feb 21 '11 at 16:54
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One volume. That said, it will suck. Unless your definition of "moderate" is a LOT smaller than the one of anyone professional. MODERATE servers have a small numbers directly attached discs for IO budgets. Luike I have one with 5 discs for datain a RAID 10... alone.

Note, this IS moderate. It is not small (just put it on a pc), but I have seen LARGE servers with hundreds of discs and am currently working on such asystem.

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