System and method to guarantee overwrite of expired data in a virtual tape server

• US 20030196036A1
• Filed: 04/11/2002
• Published: 10/16/2003
• Est. Priority Date: 04/11/2002
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Peake, Jonathan W., Kishi, Gregory T., Gibble, Kevin L.
• Granted Patent: US 6,983,351 B2
• Time in Patent Office: Days
• US Class Current: 711/111
• 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 3/0617 in relation to availability
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0682 Tape device

Abstract

A system and method for guaranteeing overwrite of expired data in a media device, the data being organized according to logical units provided on media devices organized as physical volumes. The method comprises the steps of: maintaining information associated with a status of a physical volume, and updating a physical volume'"'"'s status information based upon a combination of that volume'"'"'s prior status and that volume'"'"'s current status; specifying a time duration that expired logical unit data may remain on a physical volume; based upon the volume'"'"'s updated status information, determining whether a selected volume has expired data longer than the specified time duration; and, overwriting contents of the volume having data that has expired longer than the specified time duration.

Claims

1. A method for guaranteeing overwrite of expired data in a media device, said data organized in logical units provided on media devices organized as physical volumes, said method comprising:

a) maintaining status information associated with each physical volume, and updating a physical volume'"'"'s status information based upon a combination of that volume'"'"'s prior status and that volume'"'"'s current status;

b) specifying a time duration that expired logical unit data may remain on a physical volume;

c) based upon said volume'"'"'s updated status information, determining whether a selected volume has expired data longer than said specified time duration; and

,

d) overwriting contents of said volume having data that has been expired longer than said specified time duration.

2. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 1, wherein one or more logical units are aggregated in a storage pool spanning one or more physical volumes, said method including enabling a customer to specify said time duration that expired logical unit data may remain on a physical volume associated with a storage pool.

3. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 2, wherein a prior and current status associated with a physical volume includes one selected from the group consisting of:

a scratch status indicating a volume having no useful data;

a filling status indicating that the physical volume is currently being filling with valid data information;

a 100% fall status indicating a volume is full of valid data; and

, a less than 100% full status indicating that the physical volume has a logical unit comprising data that is no longer valid.

4. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 3, wherein said step a) of maintaining information regarding the status of a physical volume further comprises:

maintaining a first status parameter indicating a time value when a physical volume transitions from a prior scratch status to a current filling status;

maintaining a second status parameter indicating a time value when that physical volume transitions from one of said scratch, filling or 100% full status, to less than 100% full status indicating presence of invalid data.

5. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 4, wherein said step of updating a physical volume'"'"'s status information includes:

updating said first status parameter associated with that volume with a time value when a combination of that volume'"'"'s prior status and that volume'"'"'s current status indicates a transition from a prior scratch status to a current filling status;

updating said second status parameter with a time value when a combination of that volume'"'"'s prior status and that volume'"'"'s current status indicates a transition from one of said scratch, filling or 100% full status, to said less than 100% full status thereby indicating presence of invalid data.

6. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 5, wherein said step a) of maintaining information regarding the status of a physical volume further comprises the step of:

maintaining a third status parameter comprising a time value indicating a said user-specified time duration value that expired logical unit data may remain on a physical volume associated with a storage pool; and

,

updating said third status parameter associated with that volume when that volume'"'"'s current status indicates a transition to a current filling status or 100% full status.

7. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 6, wherein after updating said first, second and third parameters, the step of setting said volume'"'"'s prior status to its current status.

8. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 6, wherein said determining step c) further comprises the steps of:

determining whether physical volume has an expiration limit set as indicated by said third parameter; and

, if an expiration limit has been set; and

,

determining whether an invalidation cycle has occurred as indicated by said second parameter.

9. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 8, wherein said step of determining whether an invalidation cycle has occurred as indicated by said second parameter includes the step of:

checking whether the current date and time is greater than or equal to a value of said second parameter in sum with the value of said third parameter, said volume comprising data to be overwritten when a current date and time is greater than or equal to a value of said second parameter in sum with the value of said third parameter.

10. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 8, wherein if an expiration limit has been set as indicated by said third parameter and an invalidation cycle has not occurred for a physical volume as indicated by said second parameter, the steps of:

determining whether the volume'"'"'s prior status is scratch or filling indicating that a probability exists that some data on that volume has been expired; and

, if the volume'"'"'s prior status is scratch or filling, the step of;

checking whether the current date and time is greater than or equal to a value of said first parameter in sum with the value of said third parameter, said volume comprising data to be overwritten when a current date and time is greater than or equal to a value of said first parameter in sum with the value of said third parameter.

11. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 3, wherein said step d) of overwriting contents of said volume having data that has expired longer than said specified time duration includes the steps of:

determining whether a current status of said volume is a scratch status; and

, if a current status of said volume is a scratch status, the step of;

writing a data pattern over said entire volume.

12. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 11, wherein said data pattern includes a random data pattern.

13. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 11, wherein if a current status of said volume is not a scratch status, the step of:

performing a reclamation process on said volume to render said volume'"'"'s status to scratch prior to writing said data pattern over said entire volume.

14. The method for guaranteeing overwrite of expired data in a media device as claimed in claim 11, wherein after said step d) of overwriting contents of said volume having data that has expired longer than said specified time duration, the further step of resetting values of said first, second and third volume status parameters.

15. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for guaranteeing overwrite of expired data in a media device, said data organized in logical units provided on media devices organized as physical volumes, said method steps comprising:

a) maintaining status information associated with each physical volume, and updating a physical volume'"'"'s status information based upon a combination of that volume'"'"'s prior status and that volume'"'"'s current status;

b) specifying a time duration that expired logical unit data may remain on a physical volume;

c) based upon said volume'"'"'s updated status information, determining whether a selected volume has expired data longer than said specified time duration; and

,

d) overwriting contents of said volume having data that has been expired longer than said specified time duration.

16. The program storage device readable by machine as claimed in claim 15, wherein one or more logical units are aggregated in a storage pool spanning one or more physical volumes, said method including enabling a customer to specify said time duration that expired logical unit data may remain on a physical volume associated with a storage pool.

17. The program storage device readable by machine as claimed in claim 16, wherein a prior and current status associated with a physical volume includes one selected from the group consisting of:

a scratch status indicating a volume having no useful data;

a filling status indicating that the physical volume is currently being filling with valid data information;

a 100% full status indicating a volume is full of valid data; and

, a less than 100% full status indicating that the physical volume has a logical unit comprising data that is no longer valid.

18. The program storage device readable by machine as claimed in claim 17, wherein said step a) of maintaining information regarding the status of a physical volume further comprises:

maintaining a first status parameter indicating a time value when a physical volume transitions from a prior scratch status to a current filling status;

maintaining a second status parameter indicating a time value when that physical volume transitions from one of said scratch, filling or 100% fall status, to less than 100% full status indicating presence of invalid data.

19. The program storage device readable by machine as claimed in claim 18, wherein said step of updating a physical volume'"'"'s status information includes:

updating said first status parameter associated with that volume with a time value when a combination of that volume'"'"'s prior status and that volume'"'"'s current status indicates a transition from a prior scratch status to a current filling status;

updating said second status parameter with a time value when a combination of that volume'"'"'s prior status and that volume'"'"'s current status indicates a transition from one of said scratch, filling or 100% full status, to said less than 100% full status thereby indicating presence of invalid data.

20. The program storage device readable by machine as claimed in claim 19, wherein said step a) of maintaining information regarding the status of a physical volume further comprises the step of:

maintaining a third status parameter comprising a time value indicating a said user-specified time duration value that expired logical unit data may remain on a physical volume associated with a storage pool; and

,

updating said third status parameter associated with that volume when that volume'"'"'s current status indicates a transition to a current filling status or 100% full status.

21. The program storage device readable by machine as claimed in claim 20, wherein after updating said first, second and third parameters, the step of setting said volume'"'"'s prior status to its current status.

22. The program storage device readable by machine as claimed in claim 20, wherein said determining step c) further comprises the steps of:

determining whether physical volume has an expiration limit set as indicated by said third parameter; and

, if an expiration limit has been set; and

,

determining whether an invalidation cycle has occurred as indicated by said second parameter.

23. The program storage device readable by machine as claimed in claim 22, wherein said step of determining whether an invalidation cycle has occurred as indicated by said second parameter includes the step of:

checking whether the current date and time is greater than or equal to a value of said second parameter in sum with the value of said third parameter, said volume comprising data to be overwritten when a current date and time is greater than or equal to a value of said second parameter in sum with the value of said third parameter.

24. The program storage device readable by machine as claimed in claim 22, wherein if an expiration limit has been set as indicated by said third parameter and an invalidation cycle has not occurred for a physical volume as indicated by said second parameter, the step of:

determining whether the volume'"'"'s prior status is scratch or filling indicating that a probability exists that some data on that volume has been expired; and

, if the volume'"'"'s prior status is scratch or filling, the step of;

checking whether the current date and time is greater than or equal to a value of said first parameter in sum with the value of said third parameter, said volume comprising data to be overwritten when a current date and time is greater than or equal to a value of said first parameter in sum with the value of said third parameter.

25. The program storage device readable by machine as claimed in claim 17, wherein said step d) of overwriting contents of said volume having data that has expired longer than said specified time duration includes the steps of:

determining whether a current status of said volume is a scratch status; and

, if a current status of said volume is a scratch status, the step of;

writing a data pattern over said entire volume.

26. The program storage device readable by machine as claimed in claim 25, wherein said data pattern includes a random data pattern.

27. The program storage device readable by machine as claimed in claim 25, wherein if a current status of said volume is not a scratch status, the step of:

performing a reclamation process on said volume to render said volume'"'"'s status to scratch prior to writing a data pattern over said entire volume.

28. The program storage device readable by machine as claimed in claim 25, wherein after said step d) of overwriting contents of said volume having data that has expired longer than said specified time duration, the further step of resetting values of said first, second and third volume status parameters.

29. A virtual tape storage system comprising tape media devices for storing customer data organized according to one or more logical units provided on said tape media devices, said tape media devices further organized as physical volumes, said system comprising:

a) a host system interface for receiving customer instructions that specify a time duration that expired logical unit data for that customer may remain on a physical volume;

b) a control device for maintaining status information associated with each physical volume, and updating a physical volume'"'"'s status information based upon a combination of that volume'"'"'s prior status and that volume'"'"'s current status;

c) means for determining whether a selected physical volume includes expired data longer than said specified time duration; and

,

d) means for overwriting contents of said volume having data that has been expired longer than said specified time duration, wherein overwriting of expired data in a tape media device is guaranteed.