Dell SRDF Introduction

SRDF modes of operation

SRDF modes of operation address different service level requirements and determine:

• How R1 devices are remotely mirrored across the SRDF links.
• How I/Os are processed.
• When the host receives acknowledgment of a write operation relative to when the write is replicated.
• When writes “owed” between partner devices are sent across the SRDF links.

The mode of operation may change in response to control operations or failures:

• The primary mode (synchronous or asynchronous) is the configured mode of operation for a given SRDF device, range of SRDF devices, or an SRDF group.
• The secondary mode is adaptive copy. Adaptive copy mode moves large amounts of data quickly with minimal host impact. Adaptive copy mode does not provide restartable data images at the secondary site until no new writes are sent to the R1 device and all data has finished copying to the R2.

Use adaptive copy mode to synchronize new SRDF device pairs or to migrate data to another array. When the synchronization or migration is complete, you can revert to the configured primary mode of operation.