Method of and apparatus for automatic recovery of a cache in a storage system

Claim 2

A cache initialization method for use in a disk controller of a disk system, which operates under control of a host computer and includes a processor, a cache connected to said processor, and at least one storage path for controlling data transfer between said cache, said processor and a disk unit connected to said disk controller, comprising the steps of: (a) partitioning the memory area of said cache into sub-parts for purposes of initializing the cache; (b) generating a request for cache activation when said processor operates to effect data transfer between said host computer and said disk unit with said cache being unused; (c) checking whether a read/write request to said disk unit has been issued from said host computer; and (d) when there is a request for cache activation and while said disk system is operating on-line to effect data transfers between said host computer and said disk unit in response to input/output requests from said host computer, initializing a sub-part of the memory area of said cache in response to said activation request, when a read/write request from said host computer is not awaiting processing, and activating at least said sub-part of said memory area of said cache which has been initialized after the initialization thereof has been completed, thereby effecting automatic recovery of said cache without interrupting on-line operations with said host computer.

Claim 3

A method according to claim 1, wherein the entire memory area of said cache is partitioned into said plurality of sub-parts, each sub-part being of a size which can be initialized within a time period which is sufficiently short that no time-out error will result if the host computer issues a read/write request during step (c).

Claim 4

A method according to claim 1, wherein each of said plurality of sub-parts of the memory area of said cache has an initialization time which is shorter than the time allowed for a read/write request waiting time.

Claim 5

A method according to claim 1, further comprising the steps of: (e) repeating step (b) subsequent to step (d) and processing a read/write request from said host computer if a read/write request is awaiting processing; and (f) if step (e) indicates that a read/write request from the host computer is not awaiting processing, repeating steps (d) and (e) to initialize and activate another sub-part of the memory area of said cache until all sub-parts of the memory area have been initialized and activated.

Claim 6

A method according to claim 4, wherein said disk system is connected with a service processor, wherein the step (b) of generating a cache activation request is effected through said service processor after the repairing of a failure of said cache memory, and includes returning an acknowledge signal to said service processor from said disk system to acknowledge the cache activation request from said service processor; and further including the step of: (g) communicating to said service processor the completion of cache initialization and cache activation or communicating failure of said cache activation due to occurrence of a failure.

Claim 7

A method according to claim 5, further comprising the step of: (h) maintaining and controlling said cache, after having communicated a failure to said service processor, when a failure occurs in operation of said cache.

Claim 8

A method according to claim 1, wherein said step (c) comprises examining whether or not there is a read/write request for said disk unit from said host computer at every lapse of a constant time counted by a timer disposed in said disk system; and performing step (d) for initializing a sub-part of said memory area of said cache when no read request is found in step (c).

Claim 9

A method according to claim 1, wherein said disk system includes a plurality of storage paths and said processor is a control processor for controlling said storage paths, wherein step (d) comprises: initializing a sub-part of the memory area of said cache using said control processor, when said control processor is not executing a read/write request of said disk unit, in response to the cache activation request which is generated when said control processor is operating without using said cache.

Claim 10

A method according to claim 1, wherein said step (b) comprises: deciding whether or not a failure of said disk system is a hardware failure of said cache itself when it occurs during an access to said cache; deciding whether or not management information of the data in said cache is being updated; and prohibiting use of said cache temporarily, by said disk system, for a failure in which the hardware of said cache itself is normal and in which the management information of the data in said cache is being updated.

Claim 11

A method according to claim 9, wherein said disk system includes a plurality of storage paths and a plurality of control processors for controlling said storage paths, further comprising the step of: initializing a sub-part of said memory area of said cache in step (c) after it has been confirmed that all of said control processors have stopped using said cache.

Claim 12

A disk controller for a disk system, which disk controller operates under control of a host computer and includes a processor, a cache connected to said processor, and at least one storage path for controlling data transfer between said cache, said processor and a disk unit connected to said disk controller, comprising: means for partitioning the memory area of said cache into sub-parts for purposes of initializing the cache; means for generating a request for cache activation when said processor operates to effect data transfer between said host computer and said disk unit with said cache being unused; means for checking whether a read/write request to said disk unit has been issued from said host computer; means for initializing a sub-part of the memory area of said cache, in response to said activation request, when a read/write request from said computer is not awaiting processing and while said disk system is operating on-line to effect data transfers between said host computer and said disk unit in response to input/output requests from said host computer; means for activating at least said sub-part of said memory area of said cache which has been initialized after the initialization thereof has been completed and while said disk system is still operating on-line with said host computer, thereby effecting automatic recovery of said cache without interrupting on-line operations with said host computer; and means for operating said checking means after said initialization and activation of a sub-part of said memory area of said cache has been completed and for processing a read/write request before a further sub-part is initialized if the presence of a read/write request is indicated by said checking means.

Claim 13

A disk controller for a disk system, which disk controller operates under control of a host computer and includes a processor, a cache connected to said processor, and at least one storage path for controlling data transfer between said cache, said processor and a disk unit connected to said disk controller, comprising: means for partitioning the memory area of said cache into sub-parts for purposes of initializing the cache; means for generating a request for cache activation when said processor operates to effect data transfer between said host computer and said disk unit with said cache being unused; means for checking whether a read/write request to said disk unit has been issued from said host computer; means for initializing a sub-part of the memory area of said cache, in response to said activation request, when a read/write request from said computer is not awaiting processing and while said disk system is operating on-line to effect data transfers between said host computer and said disk unit in response to input/output requests from said host computer; means for activating at least said sub-part of said memory area of said cache which has been initialized after the initialization thereof has been completed and while said disk system is still operating on-line with said host computer, thereby effecting automatic recovery of said cache without interrupting on-line operations with said host computer; and means for operating said checking means after said initialization and activation of a sub-part of said memory area of said cache has been completed and for processing a read/write request before a further sub-part is initialized if the presence of a read/write request is indicated by said checking means.

Claim 14

A disk controller according to claim 11, wherein the entire memory area of said cache is partitioned into said plurality of sub-parts, each sub-part being of a size which can be initialized within as time period which is sufficiently short that no time-out error will result if the host computer issues a read/write request during initialization.

Claim 15

A disk controller according to claim 11, further comprising: means for deciding whether or not a failure of said disk system is a hardware failure of said cache itself when a failure occurs during an access to said cache; means for deciding whether or not management information of data in said cache is being updated; means for prohibiting use of said cache temporarily, by said disk system, upon occurrence of a failure in which the hardware of said cache itself is normal and in which management information of data in said cache is being updated.

Claim 16

A disk controller according to claim 13, wherein said disk means further comprises a plurality of storage paths; a plurality of control processors for controlling said storage paths; and means for initializing a sub-part of said memory area of said cache after it has been confirmed that all of said control processors have stopped use of said cache.