Maintaining consistency for remote copy using virtualization

• US 7,660,958 B2
• Filed: 11/06/2008
• Issued: 02/09/2010
• Est. Priority Date: 01/09/2004
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Shackelford, David Michael, McBride, Gregory Edward
• Primary Examiner(s): Shah; Sanjiv
• Assistant Examiner(s): Campos; Yaima
• Application Number:
  US12/266,408
• Publication Number:
  US 20090055610A1
• Time in Patent Office: 460 Days
• Field of Search: 711/141, 711161-162, 711/202, 711/210, 711/221, 707200-206
• US Class Current: 711/162
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99954 Version management

Abstract

Provided are a system and article of manufacture for copying storage, wherein a first unit receives data updates from a second unit. The data updates are stored in a plurality of physical storage locations associated with the first unit. Links are generated to at least one of the plurality of physical storage locations to achieve consistent data between the first unit and the second unit.

Claims

1. A system for copying storage, comprising:

a memory; and

a processor coupled to the memory, wherein the processor performs operations, the operations comprising;

receiving, at a first unit, data updates from a second unit;

storing the data updates in a plurality of physical storage locations associated with the first unit, wherein the received data updates are stored only once in the plurality of physical storage locations associated with the first unit; and

generating links to at least one of the plurality of physical storage locations to achieve consistent data between the first unit and the second unit, wherein the operations further comprise;

(i) determining if the stored data updates form a consistency group, prior to generating the links, wherein the consistency group is a set of data updates in which the set of data updates corresponds to a plurality of storage volumes, wherein the set of data updates must be written together in order to maintain mutual data consistency among data included in each storage volume of the plurality of storage volumes;

(ii) determining the at least one physical storage location that commits the consistency group, wherein virtual storage associated with the first unit links to the determined at least one physical storage location, wherein a consistency group pointer table includes entries for a virtual block and a physical block; and

(iii) releasing unlinked physical storage locations to be used for storing subsequent data updates, wherein the first unit is a secondary storage control, wherein the second unit is a primary storage control, wherein the secondary storage control and the primary storage control comprise a plurality of storage controls, and wherein in response to receiving an error while waiting for all links to be updated, performing for each storage control of the plurality of storage controls being processed;

(a) determining, by a replication management application, if selected links correspond to a current consistency group for the storage control being processed; and

(b) reverting the selected links to correspond to a previous consistency group, in response to determining by the replication management application that the selected links correspond to the current consistency group for the storage control being processed.

2. The system of claim 1, wherein the secondary storage control is coupled to a secondary storage and the primary storage control is coupled to a primary storage, wherein the plurality of physical storage locations are associated with the secondary storage, and wherein the data updates are received asynchronously at the first unit.

3. The system of claim 1, wherein an application sends input/output requests to the primary storage control, wherein the data updates correspond to output requests from the application, and wherein the data updates are stored only once at the secondary storage control, wherein the secondary storage control can substitute the primary storage control in responding to the input/output requests from the application at any point in time, and wherein data in the primary and secondary storage controls are consistent at all points in time.

4. The system of claim 1, further comprising:

maintaining a data structure that maps virtual storage locations to the at least one of the plurality of physical storage locations, wherein the generated links are associated with the data structure, and wherein a plurality of applications are capable of performing input/output operations with the virtual storage locations, wherein a plurality of consistency group pointers, consistency group pointer tables, and relative times for data updates are maintained.

5. The system of claim 1, further comprising:

maintaining data structures representing consistency groups corresponding to the data updates, wherein the maintained data structures are capable of pointing to the plurality of physical storage locations, wherein a plurality of consistency group pointers, consistency group pointer tables, and relative times for data updates are maintained; and

deleting a first data structure that represents a first consistency group in response to first data updates associated with the first consistency group being committed.

6. A computer readable storage medium including code for copying to a first unit from a second unit, wherein the code when executed by a machine is capable of causing operations, the operations comprising:

receiving, at the first unit, data updates from the second unit;

storing the data updates in a plurality of physical storage locations associated with the first unit, wherein the received data updates are stored only once in the plurality of physical storage locations associated with the first unit; and

generating links to at least one of the plurality of physical storage locations to achieve consistent data between the first unit and the second unit, wherein the operations further comprise;

(i) determining if the stored data updates form a consistency group, prior to generating the links, wherein the consistency group is a set of data updates in which the set of data updates corresponds to a plurality of storage volumes, wherein the set of data updates must be written together in order to maintain mutual data consistency among data included in each storage volume of the plurality of storage volumes;

(ii) determining the at least one physical storage location that commits the consistency group, wherein virtual storage associated with the first unit links to the determined at least one physical storage location, wherein a consistency group pointer table includes entries for a virtual block and a physical block; and

(iii) releasing unlinked physical storage locations to be used for storing subsequent data updates, wherein the first unit is a secondary storage control, wherein the second unit is a primary storage control, wherein the secondary storage control and the primary storage control comprise a plurality of storage controls, and wherein in response to receiving an error while waiting for all links to be updated, performing for each storage control of the plurality of storage controls being processed;

(a) determining, by a replication management application, if selected links correspond to a current consistency group for the storage control being processed; and

(b) reverting the selected links to correspond to a previous consistency group, in response to determining by the replication management application that the selected links correspond to the current consistency group for the storage control being processed.

7. The computer readable storage medium of claim 6, wherein the secondary storage control is coupled to a secondary storage and the primary storage control is coupled to a primary storage, wherein the plurality of physical storage locations are associated with the secondary storage, and wherein the data updates are received asynchronously at the first unit.

8. The computer readable storage medium of claim 6, wherein an application sends input/output requests to the primary storage control, wherein the data updates correspond to output requests from the application, and wherein the data updates are stored only once at the secondary storage control, wherein the secondary storage control can substitute the primary storage control in responding to the input/output requests from the application at any point in time, and wherein data in the primary and secondary storage controls are consistent at all points in time.

9. The computer readable storage medium of claim 6, further comprising:

maintaining a data structure that maps virtual storage locations to the at least one of the plurality of physical storage locations, wherein the generated links are associated with the data structure, and wherein a plurality of applications are capable of performing input/output operations with the virtual storage locations, wherein a plurality of consistency group pointers, consistency group pointer tables, and relative times for data updates are maintained.

10. The computer readable storage medium of claim 6, further comprising:

maintaining data structures representing consistency groups corresponding to the data updates, wherein the maintained data structures are capable of pointing to the plurality of physical storage locations, wherein a plurality of consistency group pointers, consistency group pointer tables, and relative times for data updates are maintained; and

deleting a first data structure that represents a first consistency group in response to first data updates associated with the first consistency group being committed.