I received some questions today around the storage latency requirements for vSphere Metro Storage Cluster (vMSC) solutions. In the past the support limits were strict:
- 5ms RTT for vMotion for Enterprise license and lower, 10ms RTT for vMotion for Enterprise plus
- 5ms RTT for storage replication
RTT stands for Round Trip Time by the way. Recently, and today I noticed I never blogged about this, the support limits have changed. For instance EMC VPLEX supports up to 10MS RTT for vMotion (not fully tested for stretched cluster / vSphere HA). Which indeed makes a lot of sense to have it aligned with the vMotion limits as more than likely the same connection between sites is used for both storage replication and vMotion traffic.
So I would recommend anyone who is considering implementing a vMSC environment (or architecting one) to contact your storage vendor about their support limits when it comes to storage latency.