Patent ID: 8527467

Claim:
A method, comprising: assigning, to each tier in a storage system comprising multiple tiers, a respective range of priority scores, each range being continuous and non-overlapping, the multiple tiers including a higher performance storage tier and a lower performance storage tier; calculating a compression ratio for a file stored on one of the multiple tiers; calculating, using the compression ratio, a priority score for the file, wherein a higher compression ratio indicates less compressible data and a lower compression ratio indicates more highly compressible data, the priority score (P) is represented by P=α*C+(1−α)*F, where C is the compression ratio, F is the usage frequency, α is a tunable parameter configured to set weights for the compression ratio and the usage frequency, and 0<α<1; and based on the priority score calculated for the file, migrating the file to the tier whose assigned range of priority scores includes the calculated priority score, wherein the higher performance storage tier is assigned a first range of priority scores including the higher compression ratio to thereby store the less compressible data, and the lower performance storage tier is assigned a second range of priority scores including the lower compression ratio to thereby store the more highly compressible data.