Modes
Modes of operation
Each SRDF base solution operates in one of the following modes of operation:
- synchronous
- semi-synchronous
- adaptive copy
- asynchronous.
Adaptive copy
SRDF supports adaptive copy write pending and adaptive copy disk modes as secondary modes of operation. Adaptive copy modes allow the R1 and R2 devices to be more than one I/O out of synchronization. Unlike the asynchronous mode, adaptive copy modes do not guarantee a dependent-write consistent copy of data on R2 devices. The amount of data (number of tracks) out of synchronization between the R1 and the R2 devices at any given time is determined by the maximum skew value. You can set the maximum skew value by using EMC host-based SRDF software. As secondary modes of operation, adaptive copy modes revert to the specified primary mode of operation, which is either synchronous mode or semi-synchronous mode, when certain conditions are met.