It may be that you've reached the point of your VMware implementation that you need to break your machines into separate clusters.
The proposed solution above will work without breaking your cluster, but does have some limits. Depending on your scenario, it may be that you can separate your ESX machines into a 3 machine cluster and a 13 machine cluster (depending on how it works, you may shrink your remaining cluster too).
It is carving up your resources a bit, but the only limit in this case is that the DRS wouldn't automatically move machines between the group of 3 and 13 (which is what you want for windows). However, you still would be able to manually vmotion things between the clusters if you need to.
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by: davismisbehavisPosted on 2009-05-09 at 12:39:12ID: 24345316
I'm presuming that when you talk about vmotion, you mean DRS movement of these windows boxes around the 16 hosts in the cluster. The problem is that you can't really associate VM's with hosts unless you use CPU affinity and this then ties you to a single host and unfortunately a 1:1 assocation with the CPU which is not the best for CPU scheduling at the vmkernel level.
What you could do though is create 3 Dummy VM's (no disks, min memory, etc) on the 3 hosts you have licensed for windows data centre, create them on local disk as opposed to on the SAN that way they can't be vmotioned. Create an DRS affinity between 4 of your windows VM's and the dummy VM that is stored locally and repeat this on all 3 hosts. These machines unfortunately will no longer vmotion as part of DRS but you have manually load balanced them already across the 3 hosts. Other machines not associated with the dummy VM's on the same hosts will vmotion off if there is resource contention so that should stop any issues and ensure that your windows servers don't suffer.
If you've got HA on your cluster then you should be protected for any host failure scenario. This should allow you to confine everything to 3 hosts and keep the costs down, hope this helps.
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