Segmenting cache to provide varying service levels

(54) SEGMENTING CACHE TO PROVIDE VARYING SERVICE LEVELS

(75) Inventors: Daniel Lambright, Watertown, MA (US); Adi Ofer, Wellesley, MA (US); Natan Vishlitzky, Brookline, MA (US); Yuval Ofek, Framingham, MA (US)

(73) Assignee: EMC Corporation, Hopkinton, MA (US)

( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/535,134

(22) Filed: Mar. 24, 2000

Related U.S. Application Data

(63) Continuation-in-part of application No. 09/434,611, filed on Nov. 5, 1999, now Pat. No. 6,457,102.

(51) Int. CI.7 G06F 12/08

(52) U.S. C I 711/129

(58) Field of Search 711/113, 118,

711/129, 153, 173; 707/101

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OTHER PUBLICATIONS

"Cache memories quicken access to disk data"; 2328 Electronic Design; vol. 30(1982) May, No. 10, Waseca, MN Denville, NJ "Systems and Software".

* cited by examiner

Primary Examiner—Hiep T. Nguyen

(74) Attorney, Agent, or Firm—Choate, Hall & Stewart

(57) ABSTRACT

Storing data in a cache memory ol a storage device includes providing access to a first segment ol the cache memory on behall ol a first group ol external host systems coupled to the storage device and providing access to a second segment ol the cache memory on behall ol a second group ol external host systems coupled to the storage device, where at least a portion ol the second segment ol the cache memory is not part ol the first segment ol the cache memory. In some embodiments, no portion ol the second segment ol the cache memory is part ol the first segment. Storing data in a cache memory ol a storage device may also include providing a first data structure in the first segment ol the cache memory and providing a second data structure in the second segment ol the cache memory, where accessing the first segment includes accessing the first data structure and accessing the second segment includes accessing the second data structure. The data structures may be doubly linked ring lists ol blocks ol data. Each block ol data may correspond to a track on a disk drive. Different groups ol external host systems may be provided with different access, priority, and level ol service with respect to the different segments ol the cache.

18 Claims, 9 Drawing Sheets