Access commands including expected media positions

Patent metadata

Field	Value
Publication number	US-9875026-B2
Application number	US-201113171888-A
Country	US
Kind code	B2
Filing date	Jun 29, 2011
Priority date	Jun 29, 2011
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

Techniques to send and receive access commands are provided. The access commands may include an expected media position. The expected media position may be compared to an actual media position.

First claim

We claim:

1. A method comprising:
including an expected media position in an access command sent from a device driver of a computer to a sequential access storage device, the expected media position calculated by the device driver; and
receiving a response from the sequential access storage device indicating if the expected media position matches an actual media position.

2. The method of claim 1 wherein the response indicating a successful completion of the access command indicates matching expected and actual media positions.

3. The method of claim 1 further comprising:
sending a media positioning command to the sequential access storage device if the response indicates the expected and actual media positions do not match; and
reissuing the access command with the expected media position.

4. The method of claim 1 further comprising:
recalculating, with the device driver, the expected media position upon successful completion of the access command based on the access command that was just completed.

5. The method of claim 1 further comprising:
detecting a communications path failure between the computer and the sequential access storage device; and
switching to an alternate communications path.

6. The method of claim 1 wherein the expected and actual media positions identify physical locations on the media.

7. The method of claim 1 wherein the expected and actual media positions represent logical locations on the media.

8. A non-transitory computer readable medium containing thereon a set of instructions which when executed by a computer cause the computer to:
send an access command to a sequential access storage device over a first communications path;
determine a failure of the access command; and
resend the access command to the sequential access storage device over a second communications path, the access command including an expected media position, the expected media position calculated by a device driver.

9. The non-transitory medium of claim 8 further comprising instructions which cause the computer to:
receive a response from the sequential access storage device over the second communications path indicating successful completion of the access command, wherein successful completion indicates the expected media position matches an actual media position.

10. The non-transitory medium of claim 8 further comprising instructions which cause the computer to:
receive a response from the sequential access storage device over the second communications path indicating the expected media position does not match an actual media position;
send a media positioning command to the sequential access storage device to position the media at the expected media position; and
resend the access command to the sequential access storage device over the second communications path.

11. The non-transitory medium of claim 8 further comprising instructions which cause the computer to:
calculate the expected media position based on successfully completed access commands.

12. The non-transitory medium of claim 8 further comprising, instructions which cause the computer to:
include the expected media position in all commands.

13. A device comprising:
a media access module; and
a controller coupled to the media access module to receive access commands which include an expected media position, the expected media position calculated by a device driver, and to compare the expected media position with an actual position as indicated by the media access module.

14. The device of claim 13 wherein the controller responds with an error response if the expected and actual media positions are not the same.

15. The device of claim 13 wherein the device is a tape storage device.

16. The method of claim 1 wherein the expected media position is maintained by the device driver.

17. The method of claim 1 wherein the expected media position represents the device driver's view of a current position of media in the storage device.

18. The method of claim 1 wherein the expected media position is calculated by the device driver without further input from an application, operating system, and the storage device.

19. The method of claim 1 wherein calculating the expected media position is by adding an initial position plus a number of blocks of data just written to the storage device.

20. The device of claim 13 wherein the expected media position is maintained by the device driver.

Assignees

• Ballard Curtis C
• Jones Kevin Lloyd
• Hewlett Packard Entpr Dev Lp

Inventors

• Ballard Curtis C
• Jones Kevin Lloyd

Classifications

• G06F3/0655

  Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices · CPC title

• G11B27/107

  of operating tapes · CPC title

• G06F3/0682 Primary

  Tape device · CPC title

• G06F3/0605 Primary

  by facilitating the interaction with a user or administrator · CPC title