Single Session Mode

Single session mode
SRDF/A single session mode refers to implementations where individual SRDF/A sessions, whether in the same or multiple Symmetrix arrays, have their cycle controlled independently by Enginuity rather than by EMC host-based SRDF control software.

Unlike traditional ordered write asynchronous approaches, Symmetrix arrays implement asynchronous mode host writes from the primary array to the secondary array by using dependent-write consistent delta sets:

• Enginuity groups host write I/Os into delta sets and manages dependent-write consistency for each delta set.
• Enginuity transfers these delta sets by using cycles of operation, one cycle at a time, between the primary array and the secondary array.

With Enginuity version 5x71 and higher, multiple SRDF groups can be enabled for SRDF/A operations within the same Symmetrix array. However, if multiple groups within the same Symmetrix array are enabled for SRDF/A, these sessions operate without knowledge of each other, or of SRDF/A sessions in other Symmetrix arrays.

To manage multiple SRDF/A sessions that need to be consistent, a multi session mode is required and EMC host-based SRDF software to performs this multi session management.