VMware has updated its Configuration Maximums support document (one of my favorite most documents in the VMware document library). Most notable is the increase in number of supported virtual CPUs per core:

• Previously, ESX and ESXi 3.5 Update 2 and earlier supported 8 virtual CPUs per core and in special cases, 11 virtual CPUs per core if the workloads were VDI
• The new version of the document shows ESX and ESXi 3.5 Update 3 and later support 20 virtual CPUs per core across the board – with no special circumstances for VDI workloads

One thing to note however is the fact that the number of total virtual CPUs per host or total number of virtual machines per host did not change. They remain at 192 and 170 respectively.

So we’re not increasing the total number of VMs an ESX or ESXi host will support. VMware is saying they can support the same number of VMs and vCPUs on less physical CPU cores. This may be due to more powerful CPUs entering the market (such as the Intel Nehalem). Or maybe VMware is addressing customers who have traditionally light CPU workloads and need to reach higher CPU consolidation ratios. Or maybe it has something to do with blade servers or Cisco’s UCS (or Project California). At any rate, VMware is encouraging the virtualization of more with less. Maybe it’s an economy thing. Who knows. It’s good for us though since VMware still licenses by the socket and not the core. We can power 160 VMs with an 8 core box (dual quads or quad duals).

While we’re on the subject, is anyone coming close to 170 VMs per host? What’s the most impressive consolidation ratio you’ve seen? I’d like to hear about it. As in the Citrix world, I don’t think it’s a matter of “Do we have the hardware today to handle it?” – the answer is yes. It’s more the exposure of 170 VMs on a single host and do we want to go down that road.

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