Abstract: Providing high availability cache coherency in a distributed cache environment for a storage cluster. An extent owner node in a cluster controls extent disk requests and the locking and demotion of extent data. An extent client node may access the data but does not control destaging or locking. The extent client waits for a lock state grant prior to completing any I/O request. An extent client is allowed to receive data from a host for a write request and later let the extent owner sort out the proper cache coherency order. An extent client is not required to request a lock state change from the extent owner when a read cache hit occurs in the extent client. When a read miss occurs in an extent client, the extent client can initiate a stage request from disk and request the owner for a lock state change at a later time.

Abstract: Disclosed is a method and device adapter for managing devices in a data processing system that includes a plurality of device adapters connected for independent communication with at least one shared device (e.g. disk data storage device). The method comprises the steps of: issuing a command from a first of the plurality of adapters to the at least one shared device; setting, in the first adapter, first and second timeouts associated with the command; on expiration of the first timeout value, issuing a message from said first adapter to other(s) of the plurality of adapters to request the other adapter(s) to notify the first adapter of any work requested of the shared device by the other adapter(s); and on expiration of the second timeout value, initiating a recovery operation in the data processing system.

Abstract: Disclosed is a device adapter for controlling devices in a network comprising computer processor nodes and one or more devices, the device adapter having means for determining whether or not a device state has changed after a failure. Responsive to a determination that the device state has not changed, the adapter communicates with other device adapters in the network to reestablish permissions before resubmitting I/O requests. Responsive to a determination that the device state has changed after a failure, the adapter reintegrates itself with the other device adapters in the network before reprocessing work as necessary.

Abstract: A cache memory system comprises a cache 4, a prefetch store 5, and a memory controller 3. The controller 3 receives requests from a processor 1 for access to lines of data stored in a memory 2 and maintains priority data indicative of the relative priority of lines of data stored in the cache 4.