Recently I was doing a VMware project with 14 HA Clusters (DC) and 8 HA Clusters (DRC) . During the design considerations I wondered how many datastores should be created for Site Recovery Manager (SRM) placeholders. The placeholder is a file which holds configuration information corresponding to the Protected virtual machines.
Following VMware documentation placeholder datastores must meet certain criteria:
- for clusters, the placeholder datastores must be visible to all of the hosts in the cluster.
- you cannot select replicated datastores as placeholder datastores.
When we design placeholder datastores, generally we have 3 options:
- dedicated placeholder datastore for cluster HA.
- shared placeholder datastore across clusters HA.
- 2 SRM placeholders datastore: 1 for each site.
If you have only one cluster HA per site, the answer is simple: one placeholder datastore for site. So what if you have more clusters? It depends on (e.g. size of infrastructure) - there is no technical limitation to share datastores across clusters so I create shared placeholder datastore because it is easier for administering. Sometimes creating shared datastores is limited e.g. the project I mentioned at the beginning of this article - I have a customer where sharing datastore across cluster is prohibited (security regulations).
Note: I have met SRM configuration with placeholders located at the same datastore with VM files! Of course it is NOT RECOMMENDED but also possible configuration...
