Data is mirrored directly from
subsystem to subsystem
No host processing involved
Impact on application
performance depends upon
(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
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.