International Business Machines Corporation

International Business Corporation

Machines Corporation

Kyler A Anderson

Lokesh M Gupta

Kevin J Ash

Matthew G Borlick

Matthew J Kalos

Beth Ann Peterson

Joseph Hayward

Brian Anthony Rinaldi

Jared Michael Minch

Gail Andrea Spear

Chung Man Fung

Susan Kay Candelaria

Micah Robison

Edward Lin

David Brent Schreiber

Trung Ngoc Nguyen

Warren Keith Stanley

Christopher Daniel Filachek

Mark A Lehrer

A computational device receives an indication that specifies a maximum retention time in cache for a first plurality of tracks, wherein no maximum retention time is specified for a second plurality of tracks. A plurality of insertions points are generated in a least recently used (LRU) list, wherein different insertion points in the LRU list correspond to different amounts of time that a track of the first plurality of tracks is expected to be retained in the cache, wherein the LRU list is configured to demote both tracks of the first plurality of tracks and the second plurality of tracks from the cache.

Integration of application indicated maximum time to cache to least recently used track demoting schemes in a cache management system of a storage controller

Provided are a computer program product, system, and method for using a transient cache list and prolonged cache list to manage tracks in cache based on a demotion hint with a track access request. A track is staged into the cache in response to a request for the track. A determination is made as to whether the request provides a demotion hint. The track is indicated in a transient cache list in response to determining that the request provides the demotion hint. The track is indicated in a prolonged cache list in response to determining that the request does not provide the demotion hint. The track is demoted from the cache in response to the request for the track comprising a read request, returning the track to the read request, and the track is indicated in the transient cache list.

Using a transient cache list and prolonged cache list to manage tracks in cache based on a demotion hint with a track access request

Provided are a computer program product, system, and method for indicating extents of tracks in mirroring queues based on information gathered on tracks in extents in cache. Extent information on an extent of tracks in a cache indicated in an active cache list is processed in response to destaging a track from the active cache list to add to a demote list used to determine tracks to remove from the cache. The extent information is related to a number of modified tracks in an extent destaged from the active cache list. The extent information for the extent is used to determine one of a plurality of mirroring queues to indicate the extent including modified tracks. A mirroring queue having a higher priority than another mirroring queue is processed at a higher rate to determine extents of tracks to mirror from the cache to the secondary storage.

Indicating extents of tracks in mirroring queues based on information gathered on tracks in extents in cache

Provided are a computer program product, system, and method for saving track metadata format information for tracks demoted from cache for use when the demoted track is later staged into cache. A track is demoted from the cache and indicated in a demoted track list. The track format information for the demoted track is saved, wherein the track format information indicates a layout of data in the track. The saved track format information for the demoted track is used when the demoted track is staged back into the cache.

Saving track metadata format information for tracks demoted from cache for use when the demoted track is later staged into cache

Provided are a computer program product, system, and method for determining tracks to prestage into cache from a storage. Information is provided related to determining tracks to prestage from the storage to the cache in a stage group of sequential tracks including a trigger track comprising a track number in the stage group at which to start prestaging tracks and Input/Output (I/O) activity information to a machine learning module. A new trigger track in the stage group at which to start prestaging tracks is received from the machine learning module having processed the provided information. The trigger track is set to the new trigger track. Tracks are prestaged in response to processing an access request to the trigger track in the stage group.

Dynamically determining tracks to prestage from storage to cache using a machine learning module

Provided are a computer program product for managing tracks in a storage in a cache. An active track data structure indicates tracks in the cache that have an active status. An active bit in a cache control block for a track is set to indicate active for the track indicated as active in the active track data structure. In response to processing the cache control block, a determination is made, from the cache control block for the track, whether the track is active or inactive to determine processing for the cache control block.

Maintaining an active track data structure to determine active tracks in cache to process

Provided are I/O request type specific cache directories in accordance with the present description. In one embodiment, by limiting track entries of a cache directory to a specific I/O request type, the size of the cache directory may be reduced as compared to general cache directories for I/O requests of all types, for example. As a result, look-up operations directed to such smaller size I/O request type specific cache directories may be completed in each directory more quickly. In addition, look-ups may frequently be successfully completed after a look-up of a single I/O request type specific cache directory, improving the speed of cache look-ups and providing a significant improvement in system performance. Other aspects and advantages are provided, depending upon the particular application.

I/O request type specific cache directories

Provided are a computer program product, system, and method for using a track format code in a cache control block for a track in a cache to process read and write requests to the track in the cache. A track format table associates track format codes with track format metadata. A determination is made as to whether the track format table has track format metadata matching track format metadata of a track staged into the cache. A determination is made as to whether a track format code from the track format table for the track format metadata in the track format table matches the track format metadata of the track staged. A cache control block for the track being added to the cache is generated including the determined track format code when the track format table has the matching track format metadata.

Using a track format code in a cache control block for a track in a cache to process read and write requests to the track in the cache

Using a machine learning module to dynamically determine tracks to prestage from storage to cache

A minimum retention time in cache is indicated for a first plurality of tracks, where no minimum retention time is indicated for a second plurality of tracks. A cache management application demotes a track of the first plurality of tracks from the cache, in response to determining that the track is a least recently used (LRU) track in a LRU list of tracks in the cache and the track has been in the cache for a time that exceeds the minimum retention time.

Integration of application indicated minimum time to cache to least recently used track demoting schemes in a cache management system of a storage controller

A method for maintaining statistics for data elements in a cache is disclosed. The method maintains a heterogeneous cache comprising a higher performance portion and a lower performance portion. The method maintains, within the lower performance portion, a ghost cache containing statistics for data elements that are currently contained in the heterogeneous cache, and data elements that have been demoted from the heterogeneous cache within a specified time interval. The method calculates a size of the ghost cache based on an amount of frequently accessed data that is stored in backend storage volumes behind the heterogeneous cache. The method alters the size of the ghost cache as the amount of frequently accessed data changes. A corresponding system and computer program product are also disclosed.

Calculating and adjusting ghost cache size based on data access frequency

A list of a first type of tracks in a cache is generated. A list of a second type of tracks in the cache is generated, wherein I/O operations are completed relatively faster to the first type of tracks than to the second type of tracks. A determination is made as to whether to demote a track from the list of the first type of tracks or from the list of the second type of tracks.

Cache management based on types of I/O operations

A computational device receives indications of a minimum retention time and a maximum retention time in cache for a first plurality of tracks, wherein no indications of a minimum retention time or a maximum retention time in the cache are received for a second plurality of tracks. A cache management application demotes a track of the first plurality of tracks from the cache, in response to determining that the track is a least recently used (LRU) track in a LRU list of tracks in the cache and the track has been in the cache for a time that exceeds the minimum retention time. The cache management application demotes the track of the first plurality of tracks, in response to determining that the track has been in the cache for a time that exceeds the maximum retention time.

Integration of application indicated minimum time to cache and maximum time to cache to least recently used track demoting schemes in a cache management system of a storage controller

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Sahuarita, AZ, United States of America

Kyler A Anderson