VMware Site Recovery Manager supports two main modes of array-based replication:
- Active/Passive: SRM coordinates with underlying array-based replication to create a copies of datastores or RDMs on the remote site. VMs are shut down and restarted on the target site. The Recovery Point Objective is not guaranteed to be zero. SRM attempts to synchronize any changes during a failover, but in the case of a site loss of the source it may not be possible. Recovery Time Objective is always non-zero, and the length depends on how much data needs to be synchronized and how large of a recovery occurs.
- Active/Active: SRM coordinates migrating VMs between vCenter environment. This implementation requires synchronous replication (all data is always in both sites) as well as active-active replication (the data is available in both sites at the same time). SRM will attempt to vMotion VMs to the remote vCenter if possible and if not will restart them on the second site otherwise. Recovery Point Objective is always zero, and Recovery Time Objective may be zero (generally in a migration or disaster avoidance scenario) or non-zero in certain disaster recovery events.
For Everpure, this means the use of ActiveCluster. ActiveCluster is enabled when a volume is placed in a pod and that pod is stretched to a second array. Any volume in a stretched pod is now both synchronously replicated and available in an active/active state (both FlashArrays can simultaneously service reads and writes for those volumes).
The 3.1 release of the Everpure SRA also supports recovery from a stretched pod to a third FlashArray. This does not leverage the stretched storage support in SRM as the recovery is an active/passive replication scenario. For details on that behavior see the SRM User Guide: Pod-based Periodic Replication SRM Workflow Behavior.