CACHING SCHEME SYNERGY FOR EXTENT MIGRATION BETWEEN TIERS OF A STORAGE SYSTEM

• US 20120239864A1
• Filed: 05/30/2012
• Published: 09/20/2012
• Est. Priority Date: 09/02/2010
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Montgomery, David, Sorenson, Todd C.
• Granted Patent: US 8,958,253 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/0875 with dedicated cache, e.g. instruction or stack
• CPC Class Codes: G06F 12/0897 with two or more cache hierarchy levels with multilevel cache hierarchies G06F12/0811
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 12/122 of the least frequently used [LFU] type, e.g. with individual count value
• CPC Class Codes: G06F 12/123 with age lists, e.g. queue, most recently used [MRU] list or least recently used [LRU] list
• CPC Class Codes: G06F 12/128 adapted to multidimensional cache systems, e.g. set-associative, multicache, multiset or multilevel
• CPC Class Codes: G06F 2212/314 In storage network, e.g. network attached cache
• CPC Class Codes: G06F 2212/451 Stack data
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0641 De-duplication techniques
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0649 Lifecycle management
• CPC Class Codes: G06F 3/0655 Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays

Abstract

A method according to one embodiment includes determining to move an extent from a source-tier in a storage system to a destination-tier in the storage system; determining whether any track from the set of tracks is presently being written to; designating to a write-stack associated with the source-tier each track that is presently being written to and designating to a read-stack associated with the source-tier remaining tracks from the set of tracks; removing oldest tracks from the read-stack and the write-stack until the read-stack and the write-stack have been depleted of tracks; when a parameter of the extent exceeds a migration threshold: populating a destination-tier cache with the tracks as they are removed from the read-stack and the write-stack using a predetermined read-to-write ratio and removing tracks from a source-tier cache that were removed from the read-stack and the write-stack; and migrating the extent from the source-tier to the destination-tier.

Claims

1. A method, comprising:

determining to move an extent from a source-tier in a storage system to a destination-tier in the storage system, wherein a set of tracks of the extent is presently being accessed;

determining whether any track from the set of tracks is presently being written to;

designating to a write-stack associated with the source-tier each track that is presently being written to and designating to a read-stack associated with the source-tier remaining tracks from the set of tracks;

removing oldest tracks from the read-stack and the write-stack until the read-stack and the write-stack have been depleted of tracks;

when a parameter of the extent exceeds a migration threshold;

populating a destination-tier cache with the tracks as they are removed from the read-stack and the write-stack using a predetermined read-to-write ratio; and

removing any tracks from a source-tier cache that were removed from the read-stack and the write-stack; and

migrating the extent from the source-tier to the destination-tier.

2. The method as recited in claim 1, wherein the extent is a contiguous block of data.

3. The method as recited in claim 1, wherein the parameter is related to a frequency of data access requests in the extent.

4. The method as recited in claim 1, wherein the read-to-write ratio is determined based on an amount of tracks in the write-stack as compared to an amount of tracks in the read-stack.

5. The method as recited in claim 1, wherein one of the destination-tier and the source-tier comprise solid state device (SSD) storage media, and wherein the other tier comprises at least one of:

SSD, hard disk drive (HDD), and magnetic tape drive storage media.