Cyclic point-in-time-copy architecture with data deduplication

• US 8,892,834 B2
• Filed: 04/28/2012
• Issued: 11/18/2014
• Est. Priority Date: 03/08/2011
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Benhase, Michael Thomas Jr., Brown, Theresa Mary, Gupta, Lokesh Mohan, Mellgren, Carol Santich
• Primary Examiner(s): CHOE, YONG J
• Application Number:
  US13/459,159
• Publication Number:
  US 20120233421A1
• Time in Patent Office: 934 Days
• Field of Search: 711/162, 711/E12.103
• US Class Current: 711/162
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A method for performing a write to a volume x in a cyclic point-in-time-copy architecture is described. In one embodiment, such a method includes determining whether the volume x has a child volume. The method then determines whether the target bit maps (TBMs) of both the volume x and the child volume are set. If the TBMs are set, the method finds a higher source (HS) volume from which to copy the desired data to the child volume. Once the HS volume is found, the method determines whether the HS volume and the child volume are the same volume. If the HS volume and the child volume are not the same volume, the method copies the data from the HS volume to the child volume. The method then performs the write to the volume x.

Claims

1. A method for performing a write to a volume x in a cyclic point-in-time-copy architecture, the method comprising:

determining whether the volume x has a child volume, wherein each of the volume x and the child volume have a target bit map (TBM) associated therewith;

determining whether the TBMs of both the volume x and the child volume are set;

if the TBMs are set, finding a higher source (HS) volume from which to copy data to the child volume, wherein finding the HS volume comprises finding a source volume associated with the volume x, determining a downstream mapping relationship between the source volume and the volume x, and determining if an upstream mapping relationship from the source volume was created after the downstream mapping relationship, wherein the source volume is determined to be the HS volume if the upstream mapping relationship from the source volume was created after the downstream mapping relationship;

determining whether the HS volume and the child volume are the same volume;

copying the data from the HS volume to the child volume if the HS volume and the child volume are not the same volume; and

performing the write on the volume x.

2. The method of claim 1, wherein the downstream mapping relationship is defined by a generation number (GN) associated with the volume x and a generation number (GN) associated with the source volume.

3. The method of claim 1, further comprising determining that the source volume is the HS volume if at least one of the following is true:

(a) the source volume is not also a target volume; and

(b) a TBM associated with the source volume is not set.

4. The method of claim 1, further comprising, if the TBM of the child volume is set and the TBM of the volume x is not set, copying data from the volume x to the child volume.

5. The method of claim 1, further comprising, if the TBM of the child volume is not set, not copying data to the child volume.