By Duncan Epping, Principal Architect, VMware
Last week I received a question about a paragraph in the vSphere 5.0 Availability Guide. This paragraph states the following:
vSphere HA and Storage vMotion Interoperability
In clusters where Storage vMotion is used extensively or where Storage DRS is enabled, VMware recommends that you do not deploy vSphere HA. vSphere HA might respond to a host failure by restarting a virtual machine on a host with an ESXi version different from the one on which the virtual machine was running before the failure. A problem can occur if, at the time of failure, the virtual machine was involved in a Storage vMotion action on an ESXi 5.0 host, and vSphere HA restarts the virtual machine on a host with a version prior to ESXi 5.0. While the virtual machine might power on, any subsequent attempts at snapshot operations could corrupt the vdisk state and leave the virtual machine unusable.
The key words in this paragraph are “prior to”. Let it be absolutely clear that in a normal situation there is absolutely no problem with Storage DRS and HA. In a mixed cluster cluster however there could be an issue when your host fails which had initiated the Storage vMotion. This does however mean that you would be running ESX / ESXi 4.1 or prior in a cluster together with ESXi 5.0 while already using Storage DRS.
I am assuming that most of you follow the best practice for upgrades. (Upgrade all components first, then enable new features / functionality.)
Needless to say that I submitted a request to have this paragraph changed to make it more obvious what the scenario is.