Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

In asynchronous mode (SRDF/A), data is transferred from the source (R1) site in predefined timed cycles or delta sets to ensure that data at the remote (R2) site is dependent write consistent.

The array acknowledges all writes to the source (R1) devices as if they were local devices. Host writes accumulate on the source (R1) side until the cycle time is reached and are then transferred to the target (R2) device in one delta set. Write operations to the target device are confirmed when the current SRDF/A cycle commits the data to disk by successfully de-staging it to the R2 storage devices.

Because the writes are transferred in cycles, any duplicate tracks written to can be eliminated through ordered write processing, which transfers only the changed tracks within any single cycle.

The point-in-time copy of the data at the secondary site is slightly behind that on the primary site.

SRDF/A has little or no impact on performance at the primary site as long as the SRDF links contain sufficient bandwidth and the secondary array is capable of accepting the data as quickly as it is being sent across the SRDF links.

When you set the mode as asynchronous for an SRDF group, all devices in the group must operate in that mode.

SRDF/Asynchronous Operations has details of all operations available for SRDF/Aysynchronous.

Example

To set the replication mode in group prod to asynchronous:

symrdf -g prod set mode async