Data storage system cluster architecture

A storage cluster includes integrated cached disk arrays (ICDAs) and cluster interconnect such as a set of Fiber Channel links. Selected ICDAs include data storage disks collectively configured as cluster volumes. A switch network in each ICDA provides connections between the cluster interconnect and host interfaces, disk interfaces, and memory modules that may reside in the ICDA. Upon receiving a request, an ICDA determines whether the target disk resides in another ICDA, and if so forwards the request to the other ICDA via the cluster interconnect. The other ICDA services the request and returns a completion indication, which is forwarded to the host. Requests may also flow from the second ICDA to the first ICDA. The ICDAs may also include memory for data caching. The switch network preferably has a common interface to the different functional elements (host interfaces, disk interfaces, memory modules) for greater flexibility in configuring each ICDA.