Increasing the speed of data migration

A system comprising:

• a processor;
• and
• a computer-readable storage medium communicatively coupled to the processor and storing program instructions which, when executed by the processor, are configured to cause the processor to perform a method comprising:
• determining a plurality of extents to migrate, wherein the plurality of extents are stored in a source tier, wherein each extent occupies an area of the source tier, and wherein the source tier is a first tier of a tiered storage;
• forming a first queue, wherein the first queue contains the plurality of extents;
• selecting a first extent from the first queue, wherein the first extent occupies a first area of the source tier;
• copying the first extent to a target tier, wherein the first extent will be copied to a first area of the target tier, wherein the target tier is a second tier of the tiered storage, the copying further comprising:
• dividing the first extent into a plurality of strides, wherein each stride is equal volume;
• forming a second queue, wherein the second queue contains the plurality of strides;
• selecting a first stride from the second queue;
• copying the first stride from the source tier to the target tier;
• and
• removing the first stride from the second queue;
• changing a volume mapping table to point to the target tier for the first extent;
• removing the first extent from the first queue;
• and
• releasing the first area of the first tier.

A computer program product, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processing unit to cause the processing unit to perform a method comprising:

• determining a plurality of extents to migrate, wherein the plurality of extents are stored in a source tier, wherein each extent occupies an area of the source tier, and wherein the source tier is a first tier of a tiered storage;
• forming a first queue, wherein the first queue contains the plurality of extents;
• selecting a first extent from the first queue, wherein the first extent occupies a first area of the source tier;
• copying the first extent to a target tier, wherein the first extent will be copied to a first area of the target tier, wherein the target tier is a second tier of the tiered storage, the copying further comprising:
• dividing the first extent into a plurality of strides, wherein each stride is equal volume;
• forming a second queue, wherein the second queue contains the plurality of strides;
• selecting a first stride from the second queue;
• copying the first stride from the source tier to the target tier;
• and
• removing the first stride from the second queue;
• changing a volume mapping table to point to the target tier for the first extent;
• removing the first extent from the first queue;
• and
• releasing the first area of the first tier.