A fiber channel storage area network (SAN) provides virtualized storage
space for a number of servers to a number of virtual disks implemented on
various virtual redundant array of inexpensive disks (RAID) devices
striped across a plurality of physical disk drives. The SAN includes
plural controllers and communication paths to allow for fail-safe and
fail-over operation. The plural controllers can be loosely-coupled to
provide n-way redundancy and have more than one independent channel for
communicating with one another. In particular, respective portions from
each of the back-end physical disk drives within the SAN are used as one
of these alternative communication channels to pass messages between
controllers. Such an alternative communications channel provides even
further redundancy and robustness in the system.
