EMC SRDF modes

PowerHA® SystemMirror® supports SRDF replicated resources in synchronous mode (SDRF/S) and in asynchronous mode (SRDF/A).

SRDF synchronous replication

In the synchronous mode, the EMC storage device responds to the host that issued a write operation to the source of the composite group after the EMC storage, which contains the target of the composite group, acknowledges that it has received and checked the data.

SRDF asynchronous replication

In the asynchronous mode, the EMC storage device provides a consistent point-in-time image on the target of the composite group, which is a short period of time behind the source of the composite group. Asynchronous mode is managed in sessions. Asynchronous mode transfers data in predefined timed cycles or in delta sets to ensure that data at the remote target of the composite group site is in the dependent write consistent state.