Data is mirrored directly from subsystem to subsystem
No host processing involved
Impact on application performance depends upon mode (synchronous or asynchronous)
e.g. EMC SRDF HDS True Copy HP Continuous Access IBM Metro Mirror / Global Mirror
If we use storage based mirroring. Here our host writes to our storage, the storage does the replication, it comes back with the acknowledgement, if its synchronous we acknowledge at that point, if it’s asynchronous we have already acknowledged and we just track it to here.
Data is mirrored directly from subsystem to subsystem, it still goes over our SAN twice, but no host processing is involved.
But as far as our systems are concerned this is proprietary. Quite often it has to be the same family to the same family not just the same vendor. When we are using subsystem replication it has to be homogeneous subsystem (like vendor to like vendor).
If you’ve got different vendor storage then the host can do the mirroring.