Virtual storage devices

• US 7,340,489 B2
• Filed: 04/10/2002
• Issued: 03/04/2008
• 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: Kopylovitz, Haim, Ofer, Adi, Vishlitzky, Natan, Moreshet, Hana
• Primary Examiner(s): Wassum; Luke S
• Application Number:
  US10/120,016
• Publication Number:
  US 20030195886A1
• Time in Patent Office: 2,155 Days
• Field of Search: 707200-204
• 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 stored data includes providing a virtual storage area having a table of pointers that point to sections of at least two other storage areas, where the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining which particular one of the other storage areas contain the data, and accessing the data on the particular one of the other storage areas using the table of pointers. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, where the virtual area device represents a copy of data of the first one of the other storage areas. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the first one of the other storage areas when the virtual storage area is initially associated with the first one of the other storage areas. The storage areas may be storage devices. The sections may be tracks.

Claims

1. A method of providing a point-in-time copy of stored data, comprising:

providing a virtual storage area having a table of pointers that point to sections of the stored data and to sections of at least one other storage area, wherein the virtual storage area contains no sections of data;

in response to a write of new data to a section of the stored data pointed to by a pointer of the table of the virtual storage area, copying the section of stored data to a section of the at least one other storage area prior to the write, causing a pointer of the virtual storage area to point to the section of the at least one other storage area, and writing the new data to the section of the stored data;

in response to a request for accessing data of the virtual storage area, determining which particular one of the other storage areas contain the data; and

accessing the data on the particular one of the other storage areas using the table of pointers.

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

associating the stored data with the virtual storage area, wherein the virtual storage area represents a copy of the stored data.

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

causing all of the pointers of the table to initially point to the stored data when the virtual storage area is initially associated with the stored data.

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

associating a data indicator with sections of the stored data, wherein the data indicator for a particular section indicates whether a write operation has been performed to the particular section after the stored data has been associated with the virtual storage area.

5. A method, according to claim 4, further comprising:

in response to a write to a first section of the stored data and the data indicator indicating that no write operation has been performed to the first section after the stored data has been associated with the virtual storage area, copying data of the first section to a second section that is on the at least one other storage area and causing a corresponding one of the pointers of the table to point to the second section.

6. A method, according to claim 5, further comprising:

following copying the data from the first section to the second section, sending status information to a device that caused the write operation to be performed.

7. A method, according to claim 5, wherein prior to copying data from the first section to the second section, the second section is maintained as a free section containing no data.

8. A method, according to claim 7, further comprising:

maintaining a doubly linked list of all free sections of the second one of the other storage areas.

9. A method, according to claim 1, wherein prior to copying data to a section of the at least one other storage area, the section of the at least one other storage area is maintained as a free section containing no data.

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

maintaining a doubly linked list of all free sections of the second one of the other storage areas.

11. A method, according to claim 1, wherein each of the sections of data is a track of data.

12. A method, according to claim 1, wherein each of the storage areas is a storage device.

13. A method of providing point-in-time copies of data stored in a data storage area, comprising:

providing a first virtual storage area having a first table of pointers that point to sections of the data storage area and to sections of at least one other storage area, wherein the first virtual storage area contains no sections of data;

in response to a write of new data to a section of the data storage area pointed to by a pointer of the first table of the first virtual storage area, copying the section of data to a section of the at least one other storage area prior to the write, causing a pointer of the first virtual storage area to point to the section of the at least one other storage area, and writing the new data to the section of the data storage area;

associating the data storage area with the first virtual storage area, wherein the first virtual storage area represents a copy of data of the data storage area at a first point in time;

providing a second virtual storage area having a second table of pointers that point to sections of the data storage area and to sections of the at least one other storage area, wherein the second virtual storage area contains no sections of data;

in response to a write to a section of the data storage area pointed to by a pointer of the second table of the second virtual storage area, copying the section of data to a section of the at least one other storage area prior to the write and causing a pointer of the second virtual storage area to point to the section of the at least one other storage area;

associating the data storage area with the second virtual storage area, wherein the second virtual storage area represents a copy of data of the data storage area at a second point in time;

in response to a request for accessing data of one of the virtual storage areas, determining which particular one of the storage areas contain the data; and

accessing the data on the particular one of the storage areas using one of the tables of pointers.

14. A method, according to claim 13, further comprising:

causing all of the pointers of the first table to initially point to sections of the data storage area when the first virtual storage area is initially associated with the data storage area; and

causing all of the pointers of the second table to initially point to sections of the data storage area when the second virtual storage area is initially associated with the data storage area.

15. A method, according to claim 14, further comprising:

associating a first data indicator with sections of the data storage area, wherein the first data indicator for a particular section of the data storage area indicates whether a write operation has been performed to the particular section after the data storage area has been associated with the first virtual storage area; and

associating a second data indicator with sections of the data storage area, wherein the second data indicator for a particular section of the data storage area indicates whether a write operation has been performed to the particular section after the second one of the other storage areas has been associated with the data storage area.

16. A method, according to claim 13, wherein the first time is the same as the second time.

17. A method, according to claim 13, wherein the first time is different from the second time.

18. A method, according to claim 13, wherein each of the sections of data is a track of data.

19. A method, according to claim 13, wherein each of the storage areas is a storage device.

20. A computer program product, comprising:

executable code that provides a virtual storage area having a table of pointers that point to sections of at least two other storage areas, wherein the virtual storage area contains no sections of data and wherein all of the pointers of the table of pointers initially point to a first one of the at least two other storage areas;

executable code that, in response to a write of new data to a section of the first one of the at least two other storage areas, copies the section of the first one of the at least two other storage areas to a section of a second one of the at least two other storage areas, causes a pointer of the virtual storage area to point to the section of the second one of the at least two other storage areas, and writes the new data to the first one of the at least two other storage areas;

executable code that determines which particular one of the at least two other storage areas contain the data in response to a request for accessing data of the virtual storage area; and

executable code that accesses the data on the particular one of the at least two other storage areas using the table of pointers.

21. A computer program product, according to claim 20, further comprising:

executable code that associates the first one of the other storage areas with the virtual storage area, wherein the virtual storage area represents a copy of data of the first one of the other storage areas.

22. A computer program product, according to claim 21, further comprising:

executable code that causes all of the pointers of the table to initially point to sections of the first one of the other storage areas when the virtual storage area is initially associated with the first one of the other storage areas.

23. A computer program product, according to claim 22, further comprising:

executable code that associates a data indicator with sections of the first one of the other storage areas, wherein the data indicator for a particular section indicates whether a write operation has been performed to the particular section after the first one of the other storage areas has been associated with the virtual storage area.

24. A computer program product, according to claim 20, further comprising:

executable code that sends status information to a device that caused the write operation to be performed following copying the data from the first section to the second section.

25. A computer program product, according to claim 20, wherein each of the sections of data is a track of data.

26. A computer program product, according to claim 20, wherein each of the storage areas is a storage device.