Query regarding RDFG mode

Hi Willy,

The Adaptive Copy Mode of operation is useful for data center migrations or for migrating large blocks of data from one place to another. When choosing this mode of synchronization, the user should be aware that data is not transferred in a serialized manner. Therefore, Adaptive Copy Mode is not a prime choice for realtime recovery.

1. Data is transferred from the source volumes to the remote volumes without waiting for an acknowledgment and allows a lag between source and target volume of a specified number of I/Os. This allows SRDF to manage the Adaptive Copy volumes at a lower priority, thus enabling applications using that volume not to encounter propagation delays while data is transferred to the remote site.

SRDF/A activation is considerate of cache utilization. SRDF/A will capture a delta set of writes and send them in cycles across the link. In addition to the new writes, SRDF/A will include up to 30,000 invalid tracks per cycle. This is a design feature and the 30,000 track value was chosen to prevent cache from being flooded by the invalid tracks. Therefore, EMC generally recommends as a best practice to synchronize the boxes in Adaptive Copy Disk mode to below 30,000 invalid tracks before activating SRDF/A. This will ensure that SRDF/A will become secondary consistent within a few cycles.