US 5,926,834 AGranted

Virtual data storage system with an overrun-resistant cache using an adaptive throttle based upon the amount of cache free space

AssigneeInternational Business Machines Corporation

InventorsWayne Charles Carlson, Gregory Tad Kishi, Jonathan Wayne Peake

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Abstract

A virtual data storage system provides a method and apparatus for adaptively throttling transfers into a cache storage to prevent an overrun in the cache storage. The virtual data storage system includes a storage interface appearing as a set of addressable, virtual storage devices, a cache storage for initially storing host-originated data files, storage devices for eventually storing the data files on a set of storage volumes, and a storage manager for directing the data files between the cache storage and the storage devices. An amount of available space in the cache storage, or a cache free space, is monitored against an adjustable cache space threshold. A storage throttle is computed when the cache free space drops below the cache space threshold. Additionally, a recall throttle is computed based on the cache free space and a number of storage devices reserved for recalling data files from the set of storage volumes. A maximum value of the storage throttle and the recall throttle is used to delay the storing of data files and the recalling of data files into the cache storage and to prevent overrunning the cache storage by completely depleting the cache free space.

Claims30

Dependent claims

A method in a virtual data storage system for adaptively throttling a transfer of data files into a cache storage to prevent overrunning said cache storage, said virtual data storage system having a storage interface appearing as a plurality of addressable virtual storage devices to a host processing system, said storage interface for receiving data files from said host processing system, and a storage manager for directing said data files between said cache storage and a plurality of storage volumes, said method comprising steps of:

(a) maintaining a cache free space within said cache storage, said cache free space defining a space within said cache storage available for storing subsequent data files;
(b) storing said data files received from said host processing system in said cache storage, said storing of data files decreasing said cache free space;
(c) migrating infrequently accessed data files from said cache storage to said plurality of storage volumes, frequently accessed data files remaining in said cache storage in anticipation of future requests from said host processing system, said migrating of data files increasing said cache free space;
(d) recalling said data files from said plurality of storage volumes to said cache storage when said host processing system requests to access one of said infrequently accessed data files, said recalling of data files decreasing said cache free space;
(e) monitoring said cache free space against a cache space threshold, said cache space threshold measuring a preferred amount of cache free space;
(f) computing a storage throttle when said cache free space decreases below said cache space threshold;
and
(g) using said storage throttle to delay said storing of data files and said recalling of data files into said cache storage to prevent overrunning said cache storage by completely depleting said cache free space.

5 more elements

A virtual data storage system receiving data files from a host processing system comprising:

a storage interface coupled to said host processing system, said storage interface appearing as a plurality of virtual storage devices to said host processing system, each said virtual storage device addressable by said host processing system;
a cache storage for initially storing said data files received from said host processing system, said cache storage including a cache free space defining a space within said cache storage available for storing subsequent data files;
a plurality of storage volumes for ultimately storing said data files as logical volumes;
and
a storage manager coupled to said storage interface, said cache storage, and said plurality of storage volumes, said storage manager directing said data files received from said host processing system into said cache storage causing said cache free space to decrease, said storage manager also migrating said data files from said cache storage to said plurality of storage volumes such that frequently accessed data files remain in said cache storage in anticipation of future requests from said host processing system, said migrating of data files increasing said cache free space, said storage manager recalling said data files from said plurality of storage volumes to said cache storage when said host processing system requests to access a previously migrated data file, said recalling of data files decreasing said cache free space, said storage manager monitoring said cache free space against a cache space threshold, said storage manager further computing a storage throttle when said cache free space decreases below said cache space threshold, said storage manager using said storage throttle to prevent overrunning said cache storage by delaying said storing of data files and said recalling of data files to said cache storage.

2 more elements

An article of manufacture for use in a virtual data storage system, said virtual data storage system having a storage interface appearing as a plurality of addressable virtual storage devices to a host processing system, said storage interface for receiving data files from said host processing system, said virtual data storage system further including a storage manager for directing said data files between a cache storage and a plurality of storage volumes, said storage manager adaptively throttling a transfer of data files into said cache storage to prevent overrunning said cache storage,

said article of manufacture comprising a computer-readable storage medium tangibly embodying a program of executable computer instructions which may cause said storage manager to:
(a) maintain a cache free space within said cache storage, said cache free space defining a space within said cache storage available for future storing of said data files;
(b) store said data files received from said host processing system into said cache storage, said storing of data files decreasing said cache free space;
(c) migrate infrequently accessed data files from said cache storage to said plurality of storage volumes, frequently accessed data files remaining in said cache storage in anticipation of future requests from said host processing system, said migrating of data files increasing said cache free space;
(d) recall said data files from said plurality of storage volumes to said cache storage when said host processing system requests to access one of said infrequently accessed data files, said recalling of data files decreasing said cache free space;
(e) monitor said cache free space against a cache space threshold, said cache space threshold measuring a preferred amount of cache free space;
(f) compute a storage throttle when said cache free space decreases below said cache space threshold;
and
(g) use said storage throttle to delay said storing of data files and said recalling of data files into said cache storage to prevent overrunning said cache storage by completely depleting said cache free space.

6 more elements

Dependencies are inferred from the claim text.