Patent ID: 7627612
Filing Date: 2009-12-01
Classification: G06F,Y10S

Abstract:
1. A method of replicating data, comprising: (a) receiving transactions comprising write data from a first data site to be backed tip at a backup storage site; (b) writing the write data to a first position in a do data stream; (c) writing metadata for the write data to a first position in a do metadata stream, wherein the metadata for the write data in step (c) comprises a first field to store a size of the write data, a second field to store an address at which the write data is to be stored in the backup storage site and a third field to store a pointer to an offset in the do data stream where the write data is located; (d) reading data from a second position in the do data stream; (e) reading metadata from a second position in the do metadata stream; (f) reading data to be overwritten from a logical unit in the backup storage site, where location and size of the data to be overwritten is determined from the do metadata stream; (g) writing the data to be overwritten to a first position in an undo data stream; (h) writing metadata for the data to be overwritten to an undo metadata stream, the metadata for the data to be overwritten comprises a first field to store a size of the data to be overwritten, a second field to store an address at which the data is to be overwritten in the backup storage site and a third field to store a pointer to an offset in the undo data stream where the data to be overwritten is located; and (i) writing the write data to the logical unit in the backup storage site using the second field in the do metadata stream.