Implementing Synchronous Data Mirroring Between FC SANs Using iSCSI Over Standard IP
Synchronous Data Mirroring is an excellent means to achieve combined Business Continuity and
Disaster Recovery. Until recently, Synchronous Mirroring was reserved as a premium feature offered
only on high-end SAN storage arrays. The proliferation of storage vendors and ultimate commoditization
of storage hardware has somewhat changed that rule, and Synchronous Mirroring options are now found on the
upper end of the mid-range market.
Synchronous Data Mirroring An Overview
Synchronous Mirroring is, in effect, an implementation of RAID-1 with the implication that the
mirrored "disks" are physically separated, either across the building, across campus or across
geographies. The data is written to both disks or volumes at once, before the write acknowledgement
is returned to requester. The principle idea is that at any given moment, the failure of a disk will
not result in a loss of any data.