Adaptive read ahead method of data recorded on a sequential media readable via a variable data block size storage device

• US 20060248278A1
• Filed: 05/02/2005
• Published: 11/02/2006
• Est. Priority Date: 05/02/2005
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Beeston, Ralph T., Smith, Cory G.
• Granted Patent: US 7,337,262 B2
• Time in Patent Office: Days
• 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 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0682 Tape device

Abstract

A read request of a sequential media from a host is executed with a read request data block size equal to a maximum recorded data block size parameter of the variable data block size storage device. Subsequently, if warranted, an adaptive read ahead data block size variable is set to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request, and one or more read ahead requests of the sequential media are executed with a read ahead data block size equal to the adaptive read ahead data block size variable. The adaptive read ahead data block size variable is conditionally adjusted based on the recorded data block size(s) of data recorded on the sequential media that is responsive to the execution(s) of the read ahead request(s)

Claims

1. A signal bearing medium tangibly embodying a program of machine-readable instructions executable by a processor to perform operations to implement an adaptive read ahead method of a sequential media readable via a variable data block size storage device, the operations comprising:

executing a read request of the sequential media in response to an electrical communication of the read request from a host, wherein the read request is executed with a read request data block size equal to a maximum recorded data block size parameter of the variable data block size storage device; and

subsequent to the execution of the read request of the sequential media, setting an adaptive read ahead data block size variable to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request.

2. The signal bearing medium of claim 1, wherein the operations further comprise:

subsequent to the execution of the read request of the sequential media, executing a read ahead request of the sequential media with a read ahead data block size equal to the adaptive read ahead data block size variable; and

subsequent to the execution of the read ahead request of the sequential media, conditionally setting the adaptive read ahead data block size variable to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request.

3. The signal bearing medium of claim 2, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

retaining the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request equals the setting of the adaptive read ahead data block size variable.

4. The signal bearing medium of claim 2, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

retaining the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable.

5. The signal bearing medium of claim 2, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

incrementing an inaccurate prediction count in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request; and

retaining the setting of the adaptive read ahead data block size variable in response to the incremented inaccurate prediction count being less than an inaccurate prediction threshold.

6. The signal bearing medium of claim 2, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

incrementing an inaccurate prediction count in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request; and

retaining the setting of the adaptive read ahead data block size variable in response to the incremented inaccurate prediction count being equal to an inaccurate prediction threshold.

7. The signal bearing medium of claim 2, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

re-executing the read ahead request of the sequential media with a read ahead data block size equal to the maximum recorded data block size parameter of the variable data block size storage device in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is greater than the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request.

8. The signal bearing medium of claim 7, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

subsequent to the re-execution of the read request of the sequential media, setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request.

9. The signal bearing medium of claim 8, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

incrementing an inaccurate prediction count subsequent to the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request; and

retaining the setting of the adaptive read ahead data block size variable response to the incremented inaccurate prediction count being less than an inaccurate prediction threshold.

10. The signal bearing medium of claim 8, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

incrementing an inaccurate prediction count subsequent to the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request; and

setting the adaptive read ahead data block size variable to equal the maximum recorded data block size of the variable data block size storage device in response to the incremented inaccurate prediction count being greater than an inaccurate prediction threshold.

11. A system, comprising:

a processor; and

a memory storing instructions operable with the processor for implementing an adaptive read ahead of a sequential media readable via a variable data block size sequential storage device, the instructions are executed for

executing a read request of the sequential media in response to an electrical communication of the read request from a host, wherein the read request is executed with a read request data block size equal to a maximum recorded data block size parameter of the variable data block size storage device; and

subsequent to the execution of the read request of the sequential media, setting an adaptive read ahead data block size variable to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request.

12. The system of claim 11, wherein the instructions are further executed for:

subsequent to the execution of the read request of the sequential media, executing a read ahead request of the sequential media with a read ahead data block size equal to the adaptive read ahead data block size variable; and

subsequent to the execution of the read ahead request of the sequential media, conditionally setting the adaptive read ahead data block size variable to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request.

13. The system of claim 12, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

retaining the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request equals the setting of the adaptive read ahead data block size variable.

14. The system of claim 12, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

retaining the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable.

15. The system of claim 12, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

incrementing an inaccurate prediction count in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request; and

retaining the setting of the adaptive read ahead data block size variable in response to the incremented inaccurate prediction count being less than an inaccurate prediction threshold.

16. The system of claim 12, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

incrementing an inaccurate prediction count in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request; and

retaining the setting of the adaptive read ahead data block size variable in response to the incremented inaccurate prediction count being equal to an inaccurate prediction threshold.

17. The system of claim 12, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

re-executing the read ahead request of the sequential media with a read ahead data block size equal to the maximum recorded data block size parameter of the variable data block size storage device in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is greater than the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request.

18. The system of claim 17, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

subsequent to the re-execution of the read request of the sequential media, setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request.

19. The system of claim 18, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

incrementing an inaccurate prediction count subsequent to the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request; and

retaining the setting of the adaptive read ahead data block size variable response to the incremented inaccurate prediction count being less than an inaccurate prediction threshold.

20. The system of claim 18, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

incrementing an inaccurate prediction count subsequent to the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request; and

setting the adaptive read ahead data block size variable to equal the maximum recorded data block size of the variable data block size storage device in response to the incremented inaccurate prediction count being greater than an inaccurate prediction threshold.

21. A method for implementing an adaptive read ahead of a sequential media readable via a variable data block size sequential storage device, the method comprising:

executing a read request of the sequential media in response to an electrical communication of the read request from a host, wherein the read request is executed with a read request data block size equal to a maximum recorded data block size parameter of the variable data block size storage device; and

subsequent to the execution of the read request of the sequential media, setting an adaptive read ahead data block size variable to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request.

22. The method of claim 21, further comprising:

subsequent to the execution of the read request of the sequential media, executing a read ahead request of the sequential media with a read ahead data block size equal to the adaptive read ahead data block size variable; and

subsequent to the execution of the read ahead request of the sequential media, conditionally setting the adaptive read ahead data block size variable to equal a recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request.

23. The method of claim 22, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

retaining the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request equals the setting of the adaptive read ahead data block size variable.

24. The method of claim 22, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

retaining the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable.

25. The method of claim 22, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

incrementing an inaccurate prediction count in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request; and

retaining the setting of the adaptive read ahead data block size variable in response to the incremented inaccurate prediction count being less than an inaccurate prediction threshold.

26. The method of claim 22, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

incrementing an inaccurate prediction count in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is less than the setting of the adaptive read ahead data block size variable equal to the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request; and

retaining the setting of the adaptive read ahead data block size variable in response to the incremented inaccurate prediction count being equal to an inaccurate prediction threshold.

27. The method of claim 22, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request includes:

re-executing the read ahead request of the sequential media with a read ahead data block size equal to the maximum recorded data block size parameter of the variable data block size storage device in response to determining the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request is greater than the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read request.

28. The method of claim 27, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

subsequent to the re-execution of the read request of the sequential media, setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request.

29. The method of claim 28, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

incrementing an inaccurate prediction count subsequent to the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request; and

retaining the setting of the adaptive read ahead data block size variable response to the incremented inaccurate prediction count being less than an inaccurate prediction threshold.

30. The method of claim 28, wherein conditionally setting the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the execution of the read ahead request further includes:

incrementing an inaccurate prediction count subsequent to the setting of the adaptive read ahead data block size variable to equal the recorded data block size of data recorded on the sequential media that is responsive to the re-execution of the read ahead request; and

setting the adaptive read ahead data block size variable to equal the maximum recorded data block size of the variable data block size storage device in response to the incremented inaccurate prediction count being greater than an inaccurate prediction threshold.