Caching scheme synergy for extent migration between tiers of a storage system and methods thereof

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.

A computer program product for re-encrypting data, the computer program product comprising:

• a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising:
• computer readable program code configured to determine 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;
• computer readable program code configured to determine whether any track from the set of tracks is presently being written to;
• computer readable program code configured to designate to a write-stack associated with the source-tier each track that is presently being written to and designate to a read-stack associated with the source-tier remaining tracks from the set of tracks;
• computer readable program code configured to remove oldest tracks from the read-stack and the write-stack until the read-stack and the write-stack have been depleted of tracks;
• computer readable program code configured to populate 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 when a parameter of the extent exceeds a migration threshold;
• computer readable program code configured to remove any tracks from a source-tier cache that were removed from the read-stack and the write-stack;
• and
• computer readable program code configured to migrate the extent from the source-tier to the destination-tier.

A storage system, comprising:

• a source-tier having storage media therein for storing data;
• a destination-tier having storage media therein for storing data;
• a source-tier cache dedicated to the source-tier;
• a destination-tier cache dedicated to the destination-tier;
• logic adapted for determining to move an extent from the source-tier to the destination-tier, wherein a set of tracks of the extent is presently being accessed;
• logic adapted for determining whether any track from the set of tracks is presently being written to;
• logic adapted for designating to a write-stack each track that is presently being written to and designating to a read-stack remaining tracks from the set of tracks;
• logic adapted for 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:
• logic adapted for populating the 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
• logic adapted for removing any tracks from the source-tier cache that were removed from the read-stack and the write-stack;
• and
• logic adapted for migrating the extent from the source-tier to the destination-tier,
• wherein the source-tier cache is used only for data stored in the source-tier,
• wherein the destination-tier cache is used only for data stored in the destination-tier,
• wherein one of the destination-tier and the source-tier comprise solid state device (SSD) storage media,
• wherein the other tier comprises at least one of:
• SSD, hard disk drive (HDD), and magnetic tape drive storage media, and
• wherein the parameter is related to a frequency of data access requests in the extent.