Immediately available, statically allocated, full-logical-unit copy with a transient, snapshot-copy-like intermediate stage

• US 6,907,505 B2
• Filed: 07/31/2002
• Issued: 06/14/2005
• Est. Priority Date: 07/31/2002
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Cochran, Robert A., Davis, Titus E.
• Primary Examiner(s): Sparks, Donald
• Assistant Examiner(s): Farrokh, Hashem
• Application Number:
  US10/209,822
• Publication Number:
  US 20040024961A1
• Time in Patent Office: 1,049 Days
• Field of Search: 711/4, 711111-112, 711/114, 711161-162, 711/210, 711/213, 707201-205
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 3/0617 in relation to availability
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A hybrid LUN copy operation that ultimately produces a full LUN copy, but involves a transient snapshot-copy-like intermediate stage. In one embodiment, a statically pre-allocated copy LUN is initialized with references pointing back to the primary LUN. Over time, the sectors, blocks, or other data-storage units of the primary LUN are copied to the copy LUN, so that, in the end, a full copy LUN in completed. In a second, alternative embodiment, both the primary LUN and copy LUN are READ and WRITE accessible immediately following the nearly instantaneous initialization of the copy LUN. In both embodiments, the copy LUN may be statically allocated. The immediate-full-LUN-copy operations provided by the present invention further enable rotatable copy-LUN groups, each copy LUN within a copy-LUN group representing a full, robust copy LUN.

Claims

1. A method for copying a logical-data-storage entity within a mass storage device, the method comprising:

providing a primary logical-data-storage entity having data-storage units;

pre-allocating a copy logical-data-storage entity having data-storage units;

initializing the copy logical-data-storage entity to contain, in each data-storage unit, an indirection indication to a corresponding data-storage unit within the primary logical-data-storage entity; and

copying data from the primary logical-data-storage entity to the copy logical-data-storage entity, overwriting the indirection indications while, at the same time, allowing READ and WRITE access to the primary logical-data-storage entity and READ access to the copy logical-data-storage entity.

2. The method of claim 1 further including, during the copy operation, allowing READ and WRITE access to both the primary logical-data-storage entity and the copy logical-data-storage entity.

3. The method of claim 1 further including allowing READ and WRITE access to both the primary logical-data-storage entity and the copy logical-data-storage entity only after the primary-logical-data-storage-entity/copy-logical-data-storage-entity is split.

4. A mass-storage-device controller that implements the method of claim 1.

5. A mass-storage device including a controller that implements the method of claim 1.

6. Computer-readable instructions that implement the method of claim 1 stored on a computer-readable medium.

7. A virtual logical-data-storage entity within a mass storage device comprising:

a primary logical-data-storage entity containing a number of data-storage units; and

a copy logical-data-storage entity containing a number of data-storage units equal to, or greater than, the number of data-storage units in the primary logical-data-storage entity, each of which initially contain an indirection indication to a corresponding data-storage unit in the primary logical-data-storage entity.

8. The virtual logical-data-storage entity of claim 7 wherein READ and WRITE operations may be directed to the primary logical-data-storage entity and READ operations may directed to the copy logical-data-storage entity while the copy logical-data-storage entity.

9. The virtual logical-data-storage entity of claim 7 wherein READ and WRITE operations may be directed to the primary logical-data-storage entity and to the copy logical-data-storage entity while the copy logical-data-storage entity.

10. The virtual logical-data-storage entity of claim 7 wherein, over time, data contained in the data-storage units of the primary logical-data-storage entity is copied to corresponding data-storage units of the copy logical-data-storage entity, overwriting the indirection indications initially stored in the data-storage units copy logical-data-storage entity.

11. The virtual logical-data-storage entity of claim 10 wherein data contained in the data-storage units of the primary logical-data-storage entity is copied only to corresponding data-storage units of the copy logical-data-storage entity that contain indirection indications.

12. A method for copying a storage entity within a mass storage device, the method comprising:

providing a primary storage entity having data-storage units;

pre-allocating a copy storage entity having data-storage units;

initializing the copy storage entity to store, associated with each data-storage unit, an indirection indication to a corresponding data-storage unit within the primary storage entity;

when a READ access directed to the copy storage entity is received and a data storage unit to which the READ access is directed references an indirection indication, reading a corresponding data storage unit on the primary storage entity; and

when a READ access directed to the copy storage entity is received and a data storage unit to which the READ access is directed does not reference an indirection indication, reading the data storage unit on the copy storage entity.

13. The method for copying a storage entity within a mass storage device of claim 12, the method further comprising:

when a WRITE access directed to the copy storage entity is received, writing data contained in the WRITE access to a storage entity to which the WRITE request was directed and updating a bit map to indicate that the storage entity has been overwritten.

14. A method for copying a storage entity within a mass storage device, the method comprising:

providing a primary storage entity having data-storage units;

pre-allocating a copy storage entity having data-storage units;

initializing the copy storage entity to store, associated with each data-storage unit, an indirection indication to a corresponding data-storage unit within the primary storage entity; and

satisfying a READ access directed to the copy storage entity from the primary storage entity if the data-storage unit to which the READ access is directed is associated with an indirection indication to the primary storage entity.

15. The method of claim 14 further including:

satisfying a READ access directed to copy storage entity from the copy storage entity if the data-storage unit to which the READ access is directed is not associated with an indirection indication to the primary storage entity.