Patent attributes
A method of operating a DSS to provision space on a volume on which a filesystem and its snapshots rest, having thin and thick files. It includes (a) receiving a reservation-altering storage command, (b) calculating a volume liability by summing together (1) a total number of allocated data blocks stored on the volume and (2) a maximum value, over each of the filesystem and the snapshots, of a difference between (A) a count of guaranteed thick blocks for that filesystem or snapshot based on a count received from the filesystem including a sum, over each thick file on the filesystem, of data blocks guaranteed to that file and (B) a number of uncompressed mapped data blocks marked as thick by the filesystem for that filesystem or snapshot, and (c) providing a number of blocks of backing store for the volume equal to at least the calculated volume liability.
