Dell PowerMax - removing volumes from SRDF groups should use "exempt" flag Edit

PowerMax allows volumes to be added, removed, or suspended without affecting the state of the SRDF/A or SRDF/Metro session or requiring that other volumes in the session be suspended. This flag is already in use when adding volumes to SRDF groups, but not when volumes are removed. This change adds usage of this flag for volume removal for the purpose of increasing the driver performance.

This change is available for SRDF groups supporting an active SRDF/A sessions or an active SRDF/Metro sessions.