Virtual storage devices

• US 7,249,130 B2
• Filed: 11/27/2002
• Issued: 07/24/2007
• Est. Priority Date: 04/10/2002
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Vishlitzky, Natan, Kopylovitz, Haim, Moreshet, Hana, LeCrone, Douglas E., Pocock, Bruce A.
• Primary Examiner(s): LEWIS, CHERYL RENEA
• Application Number:
  US10/306,378
• Publication Number:
  US 20030208463A1
• Time in Patent Office: 1,700 Days
• Field of Search: 707200-204, 707 3- 5, 707/2, 707/8, 707/100, 711/1, 711/6, 711/104, 711/113, 711/118, 711/100, 711/143
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G06F 3/0683 Plurality of storage devices
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99954 Version management

Abstract

Accessing data includes a host establishing a relationship between a first storage area of a first type containing data and a second storage area of a second type containing pointers to data provided in storage areas of the first type, where the storage areas are provided in a storage device coupled to the host. In response to the host writing data to a particular section of the first storage area after establishing the relationship, the particular section is copied from the first storage area to a third storage area of the first type prior to the write operation being executed. A corresponding pointer of the second storage area is adjusted to point to the third storage area.

Claims

1. A computer-implemented method of accessing data, comprising:

a host establishing a relationship between a first storage area of a first type containing data and a second storage area of a second type containing pointers to data provided in storage areas of the first type, wherein the storage areas are provided in a storage device coupled to the host;

in response to the host initiating a write operation to write data to a particular section of the first storage area after establishing the relationship, the particular section being copied from the first storage area to a third storage area of the first type prior to writing the data to the particular section; and

a corresponding pointer of the second storage area being adjusted to point to the third storage area.

2. A method, according to claim 1, further comprising:

restoring data from the second storage area to the first storage area.

3. A method, according to claim 1, further comprising:

restoring data from the second storage area to a fourth storage area of the first type.

4. A method, according to claim 3, wherein the fourth storage area is a split mirror of the first storage area.

5. A method, according to claim 1, wherein the first and second storage areas are storage devices.

6. A method, according to claim 5, wherein establishing a relationship includes the host providing an optional new name for the second storage device.

7. A method, according to claim 1, wherein establishing a relationship includes the host providing an optional online/offline parameter for the second storage device.

8. A method, according to claim 1, further comprising:

deactivating the second storage area by making the second storage area not available to the host.

9. A method, according to claim 8, further comprising:

making sections copied from the first storage area to the third storage area available to the host.

10. A method, according to claim 1, wherein the storage areas are devices.

11. A computer implemented method of providing a virtual storage area containing no sections of data, comprising:

providing first and second storage areas, each containing sections of data, wherein new data is written to the first storage area; and

providing a plurality of pointers, wherein each pointer points to one of;

a section of the first storage area and a section of the second storage area, wherein the virtual storage area represents a point in time copy of the first storage area and wherein, prior to writing data to a particular section of the first storage area pointed to by a particular pointer of the virtual storage area, the particular section is copied to the second storage area and the particular pointer is made to point thereto.

12. A method, according to claim 11, wherein the pointers, virtual storage area, first storage area, and second storage area are all provided on a storage device.

13. A method, according to claim 12, wherein data corresponding to the virtual storage area is accessed by a plurality of host processors coupled to the storage device.

14. A method, according to claim 11, wherein the storage areas are storage devices.

15. A computer-implemented method of accessing data stored in connection with a virtual storage area containing no sections of data, comprising:

obtaining a pointer of the virtual storage area corresponding to the data, wherein the pointer points to a first storage area if no writes have been performed to a section of the first storage area containing the data and wherein the pointer points to a second storage area if at least one write has been performed to the section of the first storage area containing the data;

in response to the pointer pointing to the first storage area, accessing the first storage area; and

in response to the pointer pointing to the second storage area, accessing the second storage area, wherein data accessed at the second storage area is a copy of data from the first storage area that was copied in response to a first write to the section of the first storage area containing the data.

16. A method, according to claim 15, wherein the pointers, virtual storage area, first storage area, and second storage area are all provided on a storage device.

17. A method, according to claim 16, wherein data corresponding to the virtual storage area is accessed by a plurality of host processors coupled to the storage device.

18. A method, according to claim 15, wherein the storage areas are devices.

19. Computer software executed in a computing device that provides a virtual storage area containing no sections of data, comprising:

executable code that provides first and second storage areas, each containing sections of data, wherein new data is written to the first storage area;

executable code that provides a plurality of pointers, wherein each pointer points to one of;

a section of the first storage area and a section of the second storage area, wherein the virtual storage area represents a point in time copy of the first storage; and

executable code that, prior to writing data to a particular section of the first storage area pointed to by a particular pointer of the virtual storage area, executable code that copies the particular section to the second storage area and adjusts the particular pointer to point thereto.

20. Computer software executed in a computing device that accesses data stored in connection with a virtual storage area containing no sections of data, comprising:

executable code that obtains a pointer of the virtual storage area corresponding to the data, wherein the pointer points to a first storage area if no writes have been performed to a section of the first storage area containing the data and wherein the pointer points to a second storage area if at least one write has been performed to the section of the first storage area containing the data;

executable code that, in response to the pointer pointing to the first storage area, accesses the first storage area; and

executable code that, in response to the pointer pointing to the second storage area, accesses the second storage area, wherein data accessed at the second storage area is a copy of data from the first storage area that was copied in response to a first write to the section of the first storage area containing the data.