Tracking Block-Level Changes Using Snapshots

A computer-readable storage medium containing instructions for causing a computer system to carry out a method of incrementally updating a backup storage volume with changes made to a source storage volume, the method comprising the steps of:

• generating a first snapshot of the source storage volume at or before the beginning of a prior backup cycle and maintaining the first snapshot through a current backup cycle;
• at the beginning of the current backup cycle, generating a second snapshot of the source storage volume and then examining a dirty block list of the first snapshot to identify a set of blocks of the source storage volume that have changed during a time period the first snapshot is maintained, the set of blocks including at least those blocks that have changed between the beginning of the prior backup cycle and the beginning of the current backup cycle;
• and
• copying the changed blocks into the backup storage volume using the second snapshot.

A computer system for tracking changes made to a source storage volume that is being backed up by a backup storage volume, comprising a processing unit that is programmed to:

• generate a first snapshot of the source storage volume at or before the beginning of a prior backup cycle and maintain the first snapshot through a current backup cycle;
• at the beginning of the current backup cycle, generate a second snapshot of the source storage volume and then examine a dirty block list of the first snapshot to identify a set of blocks of the source storage volume that have changed during a time period the first snapshot is maintained, the set of blocks including at least those blocks that have changed between the beginning of the prior backup cycle and the beginning of the current backup cycle;
• and
• copy the changed blocks into the backup storage volume using the second snapshot.