Turnover is the process of changing the primary peer in a synchronous replication scheme. The secondary peer becomes the primary peer, and the primary peer becomes the secondary peer. If both peers remain in communication with each other, the protected paths in both peers are read-writable.
Turnover is similar to failover for Asynchronous Replication, but in the case of connected peers in a Synchronous Replication scheme, there is no data loss.
Types of Synchronous Replication Turnover
Graceful Turnover
In this scenario, the roles of the primary and secondary peers are switched, with the secondary peer becoming the primary. Both remain in communication with each other, and the protected paths on both remain read-write accessible.
This is done from the VMS of the secondary peer (the peer that becomes the primary), either using the Web UI or the VCLI.
Ungraceful Turnover
In this scenario, the primary and secondary peers lose contact. As a result, the secondary peer automatically blocks access to the protected path, while the protected path on the primary peer remains read-write. This state remains until the primary peer is explicitly restored to the primary role, even if communication is restored between the peers.
Synchronous Replication Turnover Scenarios
Disconnection Between Replication Peers
In the event that communication between the replication peers is lost, the secondary peer automatically blocks access to the protected path. The primary peer automatically changes its role to standalone and maintains read-write access to the protected path.
This occurs on both peers after the sync disconnect timeout period elapses without communication between the peers.