Patent ID: 7836266
Filing Date: 2010-11-16
Classification: G06F

Abstract:
1. A method for creating snapshots for a logical volume including a plurality of partitions in a data storage system, comprising: receiving a first write command to write first data to a first physical location associated with a first address in a partition of the logical volume, the logical volume including an associated global counter configured to increment each time a snapshot is taken of the logical volume; generating a first partition descriptor record (PDR) including a first snapshot indicator, the first snapshot indicator including a same value as a first current value of the global counter; writing the first data to the first physical location; subsequent to the first write command, receiving a snapshot command to generate a first snapshot of the partition logical volume; generating the first snapshot in response to receiving the snapshot command; receiving a second write command to modify the first data; modifying the first data to create second data; comparing the first snapshot indicator and the global counter to determine if the first snapshot was generated prior to receiving the second write command; writing, based on the comparison, the second data to a second physical location in the partition and generating a second PDR including a second snapshot indicator including a same value as a second current value of the global counter for the second PDR if the global counter is greater than the first snapshot indicator; and writing, based on the comparison, the second data to the first physical location if the global counter is equal to the first snapshot indicator, wherein the second data replaces the first data at the first physical location when the global counter is equal to the first snapshot indicator.