VMware HA Admission Control

My previous article on HA failover capacity generated a bit of buzz and some discussion in the blogosphere. I have a few more details today which may clear some of the air on this.

A question was raised about the calculation used in admission control. I was previously under the impression that Configured Memory (in a VM) was the number used in this consideration. Some further investigation has revealed this is incorrect. It is the Reserved Memory, plus overhead, that is used in this calculation. VMs with no reservation still consume the overhead.

Here is vmkernel overhead-

VMware HA Admission Control

Once you have these correct numbers you can continue the calculations in my previous post.

Remember, this pertains to ESX 3.0.x and not ESX 3.5 or 3i.

These numbers have changed in VC 2.5 and ESX 3.5. It is explained in detail on page 136 – 137 (Resource Management Guide).

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