vSphere Metro Storage Clusters

Lee Dilworth
Duncan Epping

HA protects against:
- host failure
- host network isolation
- permanent loss of datastore
- VM crashes
- guest OS crash / hang
HA is OS and application independent

HA Agent is now called Fault Domain Manager and moves to a single master, multiple slave model (from 5 master model).  In the event of loss of single master, slaves elect a new master.  Heartbeating is still over the network, but now uses the datastore as an additional heartbeat to monitor.  Network heartbeat is checked first, when this is lost the datastore heartbeat is checked.

vSphere Metro Storage Cluster (essentially a stretched storage cluster)
- hardware needs to be on the HCL
- HCLs for iSCSI, NFS and FC
- network is stretched across sites
- storage is stretched across sites
- essentially a federated HA solution
- single vCenter (which can be a VM in the stretched cluster of course, and this is a common use case)
- quicker than SRM to recover machines because it is essentially an HA activity
- max supported network latency is 10ms round trip time (RTT)
- vSphere Enterprise Plus licencing is required
- max supported storage replication is 5ms RTT
- good for relatively local failover across sync sites
- most storage hardware will support an async 3rd copy of the data
- uses DRS affinity groups per site to maintain multi-tier application performance using the "should" rules, not the "must" rules.