Point in time storage copy

• US 7,290,102 B2
• Filed: 03/15/2005
• Issued: 10/30/2007
• Est. Priority Date: 06/01/2001
• Status: Expired due to Fees

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Korgaonkar, Anuja, Roberson, Randy L., Bean, Robert G., Lubbers, Clark E., Reiser, James M.
• Primary Examiner(s): PORTKA, GARY J
• Application Number:
  US11/081,061
• Publication Number:
  US 20050160243A1
• Time in Patent Office: 959 Days
• Field of Search: None
• US Class Current: 711/162
• CPC Class Codes: G06F 11/0727 in a storage system, e.g. in a DASD or network based storage system drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/0772 Means for error signaling, e.g. using interrupts, exception flags, dedicated error registers
• CPC Class Codes: G06F 11/0793 Remedial or corrective actions recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/0617 in relation to availability
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0683 Plurality of storage devices
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A storage system permits virtual storage of user data by implementing a logical disk mapping structure that provides access to user data stored on physical storage media and methods for generating point-in-time copies, or snapshots, of logical disks. A snapshot logical disk is referred to as a predecessor logical disk and the original logical disk is referred to as a successor logical disk. Creating a snapshot involves creating predecessor logical disk mapping data structures and populating the data structures with metadata that maps the predecessor logical disk to the user data stored on physical media. Logical disks include metadata that indicates whether user information is shared between logical disks. Multiple generations of snapshots may be created, and user data may be shared between these generations. Methods are disclosed for maintaining data accuracy when write I/O operations are directed to a logical disk.

Claims

1. A computer program product comprising logic instructions stored on a computer-readable medium which, when executed by a processor, configure the processor to create a point in time copy of a successor logical disk by executing operations comprising:

creating a PLDMC for a predecessor logical disk;

creating an LMAP for the predecessor logical disk;

populating the LMAP for the predecessor logical disk with one or more RSD pointers from an LMAP associated with the successor logical disk;

creating an L2MAP for the predecessor logical disk;

populating the L2MAP for the predecessor logical disk with one or more pointers to one or more predecessor LMAP records;

setting one or more share bits in the one or more LMAPs for the predecessor logical disk and the successor logical disk to indicate that the user data is being shared; and

setting one or more share bits in the successor PLDMC to indicate that the data is being shared.

2. The computer program product of claim 1, further comprising logic instructions which, when executed by the processor, configure the processor to populate the one or more LMAPs for the predecessor logical disk with one or more RSD pointers.

3. The computer program product of claim 1, further comprising logic instructions which, when executed by the processor, configure the processor to quiesce I/O operations to the successor logical disk for a predetermined period of time.

4. The computer program product of claim 3, wherein the predetermined period of time corresponds to the time required to construct the predecessor logical disk.

5. The computer program product of claim 1, further comprising logic instructions which, when executed by the processor, configure the processor to:

receive a write operation directed to memory located in an identified segment(s) of the successor logical disk; and

in response to the write operation, to;

copy the identified segment(s) to the predecessor logical disk; and

execute the write operation in the successor logical disk.

6. The computer program product of claim 5, further comprising logic instructions which, when executed by the processor, configure the processor to:

clear share bits in the one or more LMAPs for the predecessor logical disk and the successor logical disk to indicate that the identified segments are no longer being shared; and

clear share bits in the successor PLDMC to indicate that identified segments are no longer being shared.

7. A storage controller, comprising:

an first port for receiving I/O requests from one or more host computers;

a second port for transmitting I/O requests to one or more storage devices;

a processor;

a memory module connected to the processor and comprising logic instructions stored on a computer-readable medium which, when executed by the processor, configure the processor to create a point in time copy of a successor logical disk by executing operations comprising;

creating a PLDMC for a predecessor logical disk;

creating an LMAP for the predecessor logical disk;

populating the LMAP for the predecessor logical disk with one or more RSD pointers from an LMAP associated with a successor logical disk;

creating an L2MAP for the predecessor logical disk;

populating the L2MAP for the predecessor logical disk with one or more pointers to one or more predecessor LMAP records;

setting one or more share bits in the one or more LMAPs for the predecessor logical disk and the successor logical disk to indicate that the user data is being shared; and

setting one or more share bits in the successor PLDMC to indicate that the data is being shared.

8. The storage controller of claim 7, wherein the memory module further comprises logic instructions which, when executed by the processor, configure the processor to populate the one or more LMAPs for the predecessor logical disk with one or more RSD pointers.

9. The storage controller of claim 7, wherein the memory module further comprises logic instructions which, when executed by the processor, configure the processor to quiesce I/O operations to the successor logical disk for a predetermined period of time.

10. The storage controller product of claim 9, wherein the predetermined period of time corresponds to the time required to construct the predecessor logical disk.

11. The storage controller of claim 7, wherein the memory module further comprises logic instructions which, when executed by the processor, configure the processor to:

receive a write operation directed to memory located in an identified segment(s) of the successor logical disk; and

in response to the write operation, to;

copy the identified segment(s) to the predecessor logical disk; and

execute the write operation in the successor logical disk.

12. The storage controller of claim 11, wherein the memory module further comprises logic instructions which, when executed by the processor, configure the processor to:

clear share bits in the one or more LMAPs for the predecessor logical disk and the successor logical disk to indicate that the identified segments are no longer being shared; and

clear share bits in the successor PLDMC to indicate that identified segments are no longer being shared.

13. A method of creating a snapshot logical disk in a series of stacked snapshots, comprising:

creating a PLDMC for a predecessor logical disk;

creating an LMAP for the predecessor logical disk;

populating the LMAP for the predecessor logical disk with an RSD pointer from an LMAP associated with a successor logical disk;

creating an L2MAP for the predecessor logical disk;

populating the L2MAP for the predecessor logical disk with a pointer to a predecessor LMAP;

setting a share bit in the LMAP for the predecessor logical disk and in the LMAP for the successor logical disk to indicate that the user data is being shared; and

setting one or more share bits in a PLDMC associated with the successor logical disk to indicate that the data is being shared.

14. The method of claim 13, wherein the predecessor logical disk and the successor logical disk remain accessible for I/O operations.

15. The method of claim 13, further comprising:

receiving a read I/O directed to a snapshot logical disk in the series of stacked snapshots;

following a pointer in the LMAP for the predecessor logical disk and one or more successor logical disks until a clear pointer is located; and

reading a data field in the successor logical disk associated with the clear pointer.

16. The method of claim 13, further comprising:

receiving a write I/O directed to a segment in a predecessor logical disk in the series of stacked snapshots;

copying data from the segment of the predecessor logical disk to a corresponding segment in one or more successor logical disks; and

executing the write I/O against the segment of the predecessor logical disk.

17. The method of claim 13, further comprising:

receiving a write I/O directed to a segment in a successor logical disk in the series of stacked snapshots; and

following a pointer in the LMAP for the predecessor logical disk and one or more successor logical disks until a clear pointer is located; and

copying data from the segment of the successor logical disk associated with the clear pointer to a corresponding segment in one or more successor logical disks; and

executing the write I/O against the segment of the successor logical disk associated with the clear pointer.