Importance

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Abstract

Apparatus and methods which allow multiple storage controllers sharing access to common data storage devices in a data storage subsystem to access a centralized intelligent cache. The intelligent central cache provides substantial processing for storage management functions. In particular, the central cache of the present invention performs RAID management functions on behalf of the plurality of storage controllers including, for example, redundancy information (parity) generation and checking as well as RAID geometry (striping) management. The plurality of storage controllers (also referred to herein as RAID controllers) transmit cache requests to the central cache controller. The central cache controller performs all operations related to storing supplied data in cache memory as well as posting such cached data to the storage array as required. The storage controllers are significantly simplified because the present invention obviates the need for duplicative local cache memory on each of the plurality of storage controllers. The storage subsystem of the present invention obviates the need for inter-controller communication for purposes of synchronizing local cache contents of the storage controllers. The storage subsystem of the present invention offers improved scalability in that the storage controllers are simplified as compared to those of prior designs. Addition of storage controllers to enhance subsystem performance is less costly than prior designs. The central cache controller may include a mirrored cache controller to enhance redundancy of the central cache controller. Communication between the cache controller and its mirror are performed over a dedicated communication link.

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First Claim