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BP1028 EqualLogic iSCSI for Fibre Channel Professionals 8
6 Storage array architecture comparison
6.1 Fibre Channel arrays
FC storage systems have been around for over a decade and there are numerous choices when
selecting a FC environment. While these systems range from large, highly scalable models to smaller
FC arrays, many of them are monolithic designs. By that, we mean that they consist of a controller
unit (or units) that contain storage processors, cache memory, and front-end (for host/switch
connectivity) and back-end interfaces (for disks). The controller unit attaches to a disk enclosure, or
usually several disk enclosures.
Figure 3 - Monolithic Storage Architecture
When more storage capacity is needed, another disk enclosure is added to the system and new
volumes (or LUNs) can be allocated from those drives. If I/O capacity is required, the same thing
happens – or at least until the controller unit has reached its maximum potential. Sometimes this limit
is based on I/O processing limits (CPU), or there may be limitations on the number of disks an array
can support. At this point, a decision must be made to either add another controller unit (and
additional drives) or to replace the older unit with a newer, more scalable model, and migrate any
existing data.