vMotion between hosts that are in two different datacenters
A stretched VMware cluster is configured across two different datacenters/sites connected over a WAN link, and VM vmotions can happen over the WAN link between hosts at these two site locations.
If you are using ‘Write Back’ policy and if you want to support live VM vmotions between hosts across these two sites, then it is required that VirtuCache be installed on all hosts at both sites, AND there is connectivity between the two VirtuCache Replication networks at these sites. If either of these two conditions is not met, then there is a chance of data loss during a live vmotion.
However, if you will always shutdown the VM before moving it between hosts that are in different sites then the write cache will always be flushed to backend storage. So this will always be a safe operation even if you don’t have VirtuCache installed on hosts at one of your two sites.
A stretched storage cluster can be created as a single VMware cluster or two different VMware clusters across two datacenter locations. This KB applies to both situations.