Disk control device

• US 6,516,389 B1
• Filed: 09/18/2000
• Issued: 02/04/2003
• Est. Priority Date: 12/28/1999
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Digital Solutions Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Uchihori, Ikuo
• Primary Examiner(s): Nguyen, Hiep T.
• Application Number:
  US09/663,714
• Time in Patent Office: 869 Days
• Field of Search: 711/113, 711/137
• US Class Current: 711/137
• CPC Class Codes: G06F 12/0862 with prefetch
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/6024 History based prefetching

Abstract

A pre-fetch prediction table is provided for storing history of readout access given from a host device. A controller in a disk control device registers entry information including a set of an area address a indicating the access destination of the previous access and concerned prediction address b, having an area address b indicating the access destination of the readout access given from the host device as prediction address b, into a corresponding entry of the pre-fetch prediction table. Thereafter, when a readout access designating the area address a in agreement with the area address a in the concerned entry information is given from the host device, the controller pre-fetches from a HDD to a disk cache according to the prediction address b in the concerned entry information.

Claims

1. A disk control device provided with a cache memory for temporary storing a part of data on a disk device, comprising:

a readout access history table for storing history of readout access from a host computer, wherein said readout access history table has a data structure for storing in a history set including a predetermined address portion whose predetermined unit area can be designated in an access destination address information indicated by respective readout access as a first readout access history, and access destination address information of the first readout access showing an access destination address information different from said respective readout access in predetermined address portion after said respective readout access as a second readout access history;

readout access execution means for transferring data accessed by the respective readout access to the host computer using said cache memory, when said respective readout access is given from the host computer;

registration means for registering readout access history corresponding to the respective readout access by linking a previous readout history; and

pre-fetch means for pre-fetching following readout access data to said cache memory by referring the readout access history table when said following readout access data does not exist in said cache memory, wherein said pre-fetch means performs said pre-fetch according to said second readout access history among history sets having said predetermined address portion of said access destination address information indicated by said respective readout access given from said host computer as said first readout access history.

2. The disk control device according to claim 1, wherein said registration means comprises new registration means for newly registering, when a readout access different from the previous one in said predetermined address portion of access destination address information is given from said host computer and no history set including said first readout access history corresponding to a previous readout access of said given readout access exist in said readout access history table, a history set including said first readout access history corresponding to said previous readout access, and said second readout access history corresponding to said given readout access, in said readout access history table.

3. The disk control device according to claim 1, wherein said registration means comprises modification registration means for modifying, when a readout access is given from said host computer, a history set including said first readout access history corresponding to a previous readout access of said given readout access exists in said readout access history table and, at least, said second readout access history corresponding to said given readout access is not included in said history set, said second readout access history in said history set into the second readout access history corresponding to said given readout access.

4. A disk control device provided with a cache memory for temporarily storing a part of data on a disk device, comprising:

a readout access history table for storing history of readout access from a host computer wherein said readout access history table has a data structure for storing in a history set having access destination address information indicated by each readout access as a first readout access history, and access destination address information indicated by first readout access out of sequential readout beginning from said access destination address information indicated by said each readout access following said each readout access as a second readout access history, the history set including information of the number of continuous access in said sequential readout;

readout access execution means for transferring data accessed by the each readout access to the host computer using said cache memory, when said each readout access is given from the host computer;

registration means for registering readout access history corresponding to the each readout access by linking a previous readout history; and

pre-fetch means for pre-fetching following readout access data to said cache memory by referring the readout access history table when said following readout access data does not exist in said cache memory, wherein said pre-fetch means performs said pre-fetch according to said information of the number of continuous access corresponding to said second readout access history among history sets having access destination address information indicated by said each readout access given by said host computer as said first readout access history.

5. The disk control device according to claim 4, wherein said registration means, comprises new registration means for newly registering, when a readout access out of sequential readout is given from said host computer and no history set including said first readout access history corresponding to a previous readout access that is a readout access indicating access destination address information of the leading head of said sequential readout exist in said readout access history table, a history set including said first readout access history corresponding to said previous readout access, said second readout access history corresponding to said given readout access, and information of the number of continuous access in said sequential readout, in said readout access history table.

6. The disk control device according to claim 4, wherein said registration means comprises modification registration means for modifying, when a readout access out of sequential readout is given from said host computer, a history set including said first readout access history corresponding to a previous readout access that is a readout access indicating access destination address information of the leading head of said sequential readout exists in said readout access history table, and at least, said second readout access history corresponding to said given readout access is not included in the history set, said second readout access history in the history set to the second readout access history corresponding to said given readout access, and information of the number of continuous access in the history set to the information of the number of continuous access in the sequential readout.

7. The disk control device according to claim 4, further comprising sequential pre-fetch means for pre-fetching data following the data accessed by the readout access given by said host computer, according to said information of the number of continuous access stored in said readout access history table paired with said first readout access history corresponding to the readout access.

8. A disk control device provided with a cache memory for temporarily storing a part of data on a disk device, comprising:

a readout access history table for storing history of readout access from a host computer, wherein said readout access history table has a data structure for storing in a history set retaining access destination address information indicated by each readout access as a first readout access history, and retaining access destination address information indicated by the first readout access out of the sequential readout beginning from said access destination address information indicated by said each readout access, obtained after said each readout access each time said each readout access is given as a second readout access history within the upper limit of a predetermined number, the history set including information of the number of continuous access in said sequential readout;

readout access execution means for transferring data accessed by the each readout access to the host computer using said cache memory, when said readout access is given from the host computer;

registration means for registering readout access history corresponding to the each readout access by linking a previous readout history; and

pre-fetch means for pre-fetching following readout access data to said cache memory by referring the readout access history table when said following readout access data does not exist in said cache memory, wherein said pre-fetch means performs said pre-fetch according to information of the number of continuous access corresponding to all of said second readout access history among history sets having access destination address information indicated by said each readout access given by said host computer as said first readout access history.

9. The disk control device according to claim 8, wherein said registration means comprises new registration means for newly registering, when a readout access out of sequential readout is given from said host computer and no history set including said first readout access history corresponding to a previous readout access that is a readout access indicating access destination address information of the leading head of said sequential readout exists in said readout access history table, a history set including said first readout access history corresponding to said previous readout access, said second readout access history corresponding to said given readout access, and information of the number of continuous access in said sequential readout, in said readout access history table.

10. The disk control device according to claim 8, wherein said registration means comprises addition and modification means for additionally registering, when a readout access out of sequential readout is given from said host computer, a history set including said first readout access history corresponding to a previous readout access that is a readout access indicating access destination address information of the leading head of said sequential readout exists in said readout access history table, and at least, said second readout access history corresponding to said given readout access is not included in the history set, said second readout access history corresponding to said given readout access in the history set, if the number of said second readout access history included in the history set has not attained said predetermined number, and for modifying one of said second readout access history of any one of the history sets to said second readout access history corresponding to said given readout access.