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My setup up:

Dell PowerEdge M610 (6 Blades)

Three of these:

  • 2 x Intel Xeon E5540
  • 8 Physical cores
  • 16 Logical cores
  • 16 GB of RAM

Three of these:

  • 1 x Intel Xeon E5640
  • 4 Physical cores
  • 8 Logical core
  • 16 GB of RAM

Question:

Currently we have about ~13 VM servers running on these. I was wondering how many virtual machines can these physical hosts accommodate. My guestimate was about max of 4 VM servers per physical host. However, I've heard people hosting 100s of VMs on similar setup (are they exaggerating or am I being to stringent?)

If you guys need more info about my setup, I'll see what I can do. I am a Junior IT Admin, so you are more than free to commence verbose noob speak to me.

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it all depends on your workload. are you io-bound? cpu-bound? how spiky the workload is, how much over-commitment can you tolerate? start with monitoring what you have to get some idea about the baseline. – pQd Oct 16 '11 at 17:36
Will do. Wow.. I just checked a years worth of performance logs. Server 1: Max(13%), Avg(2.5%). Server 2: Max(17.9%), Avg(11%). Server 3: Max (3%), Avg(.5%). Server 4: Max(11%), Avg(5%). Server 5: Max(6.5%), Avg(1.5%). Server 6: Max(9%), Avg(5%). – Tenzin W. L. Oct 16 '11 at 19:36
Those percentages are CPU utilization. – Tenzin W. L. Oct 16 '11 at 19:58
possibly your io will be the bottle neck.. or amount of memory but it seems like you have a lot of unused hardware :p – pQd Oct 16 '11 at 20:51
We have a few of those M610's, and you're going to need a lot more than 16Gb of RAM to do any decent consolidation. Because they're half-height, you can cram twice as many in too, which is nice. – Mark Henderson♦ Oct 17 '11 at 2:24
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closed as too localized by Shane Madden, Iain♦, DJ Pon3, jscott, mailq Oct 16 '11 at 23:09

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2 Answers

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Do you have a SAN or some form of shared storage? As for capacity, it's really a function of what your guest virtual machines look like. At the minimum, calculate the RAM and CPU requirements of the guest VMs and compare against the totals from your physical hardware.

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Yea, we have a 2TB Dell PS6000e SAN. I've been allocating the physical hosts to the VMs as though they were physical computers. For instance, I use "physical cores" instead of logical cores (is that too stringent) and allocate memory without over commitment. – Tenzin W. L. Oct 16 '11 at 19:28
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up vote 0 down vote

In my previous job i worked for a web hosting company on similar hardware we hosted around 70 VPS servers (which host IIS + SQL EXP + MailEnable) which didn't really strain the CPU or memory in any way but as stated by ewwhite in the post above the real concern is the Disk I/O which will be the problem without a doubt if you don't have a storage system connected somewhere and you start adding alot more VM without checking in peak times whats the "new status" of the host.

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