Patent ID: 7930326

Claim:
A method comprising: identifying a multi-block storage region as satisfying a block vacancy criterion, the multi-block storage region being one of a plurality of multi-block storage regions of a file system in a data storage system, each multi-block storage region comprising a plurality of mass storage devices, by computing a value that represents an amount of block vacancy in said multi-block storage region based on identifying, using a block vacancy map of a current state of the file system and a block vacancy map of at least one past state of the file system, each block allocated on a mass storage device in said multi-block storage region during the current state and each block allocated on the mass storage device in said multi-block storage region during the at least one past state, and determining that the value has a particular relationship to an allocation threshold; and in response to identifying the multi-block storage region as satisfying the block vacancy criterion, selecting the multi-block storage region as a destination for data to be written.