Patent ID: 8583838

Claim:
A method for tracking and using activity information for one or more logical devices comprising: partitioning each of said one or more logical devices into one or more extents, each of said one or more extents including a plurality of sub extents, each of said sub extents including a plurality of chunks; determining, for each of said one or more extents of each of said one or more logical devices, extent activity level information including one or more metrics indicating an activity level for said each extent; determining, for each of said one or more extents of each of said one or more logical devices, an activity bitmap, said activity bitmap including an entry for each sub extent included in said each extent, said entry indicating an activity level for said each sub extent; and selecting a first sub extent of a first extent of a first of the one or more logical devices as a candidate for data movement using said extent activity level information and said activity bitmap for said first extent, said data movement being any of demotion from a first storage tier to a second storage tier whereby the first storage tier is a higher performance tier than said second storage tier, and promotion from the second storage tier to the first storage tier, said first storage tier including physical storage devices of a first storage type and said second storage tier including physical storage devices of a second storage type different than the first storage type, wherein a physical storage device of the first storage type provides higher performance than a physical storage device of the second storage type.