A couple of weeks ago I published an article on the maximum amount of VMs one could run on a ESX host. In short; if you enabled HA on your cluster it restricts the amount of VMs you can run on a host depending on the total amount of hosts in the cluster. This means that depending on your consolidation ratio you would need to limit the amount of hosts in a cluster.
Now, there might be another argument to take a good look at your cluster size. Site Recovery Manager. Currently vCenter 2.5 does not allow to simultaneously boot more than 16 VMs.
I’ve always been under the impression that the limit for SRM was 8 simultaneous boots but one of my colleagues notified me that the limit is actually 16. If all you care about is a low RTO, 16 would be a good cluster size wouldn’t it? There’s no point in having more than 16 hosts in a SRM enabled cluster if you don’t need the resources. However, don’t forget to take the HA “limitation” in account when designing your environment for availability.
Could you update this to reflect SRM 5.1 enhancements?
Further to the above request, would it be possible to get an update relevent for the latest versions of vSphere 5.5 and SRM 5.5?
Thanks.