OVERHEAD CALCULATION IN WRITING SYNCHRONIZED DATA TO MAGNETIC TAPE

• US 20110051280A1
• Filed: 08/31/2009
• Published: 03/03/2011
• Est. Priority Date: 08/31/2009
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: OISHI, Yutaka, OE, Motoko, KATAGIRI, Takashi, KARP, James M.
• Granted Patent: US 7,995,303 B2
• Time in Patent Office: Days
• US Class Current: 360/73.01
• CPC Class Codes: G11B 15/02 Control of operating function, e.g. switching from recording to reproducing
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 2220/90 Tape-like record carriers

Abstract

Various embodiments for writing received synchronized data to magnetic tape having a plurality of wraps using a magnetic tape drive adapted for performing the writing according to an available plurality of predefined tape speeds are provided. In one such embodiment, for each of the available plurality of predefined tape speeds, an average overhead per synchronized command for performing a recursively accumulated backhitchless flush (RABF) cycle is calculated. One of the available plurality of predefined tape speeds having a lowest calculated average overhead is selected. The RABF cycle is performed using the selected one of the available plurality of predefined tape speeds.

Claims

1. A method for writing received synchronized data to magnetic tape having a plurality of wraps using a magnetic tape drive adapted for performing the writing according to an available plurality of predefined tape speeds, the method comprising:

for each of the available plurality of predefined tape speeds, calculating an average overhead per synchronized command for performing a recursively accumulated backhitchless flush (RABF) cycle;

selecting one of the available plurality of predefined tape speeds having a lowest calculated average overhead; and

performing the RABF cycle using the selected one of the available plurality of predefined tape speeds.

2. The method of claim 1, further including, previous to the calculating the average overhead, detecting a pattern of synchronizing events for writing transactions to the magnetic tape, the detecting triggering a RABF mode of operation.

3. The method of claim 2, further including, pursuant to performing the RABF cycle:

accessing at least one work copy wrap of the magnetic tape with at least one read/write head of the magnetic tape drive,

writing at least one stored synchronized transaction of the detected pattern from a buffer to the at least one work copy wrap of the magnetic tape,

upon writing the at least one stored synchronized transaction from the buffer to the magnetic tape, accumulating the at least one stored synchronized transaction in the buffer, and

subsequently accessing at least one normal wrap of the magnetic tape separate from the at least one work copy wrap, and recursively writing the accumulated transactions from the buffer to the magnetic tape in a sequence.

4. The method of claim 3, further including, if the detecting triggers a first occurrence of the RABF mode of operation in a period of time, performing a first RABF cycle using a fastest tape speed of the available plurality of predefined tape speeds.

5. The method of claim 1, further including, previous to calculating the average overhead, determining if a host transfer rate is smaller than a first tape speed of the available plurality of predefined tape speeds.

6. The method of claim 5, wherein if the host transfer rate is smaller than the first tape speed, performing the calculating the average overhead for the first tape speed.

7. The method of claim 6, wherein if an additional tape speed of the available plurality of predefined tape speeds is slower than the first tape speed, determining if the host transfer rate is smaller than the additional tape speed, wherein if the host transfer rate is smaller, performing the calculating the average overhead for the additional tape speed.

8. A system for writing received synchronized data to magnetic tape having a plurality of wraps using a magnetic tape drive adapted for performing the writing according to an available plurality of predefined tape speeds, the system comprising:

at least one buffer; and

a controller coupled to and operating the at least one buffer, the controller including a processor device, wherein the controller is adapted for;

for each of the available plurality of predefined tape speeds, calculating an average overhead per synchronized command for performing a recursively accumulated backhitchless flush (RABF) cycle;

selecting one of the available plurality of predefined tape speeds having a lowest calculated average overhead; and

performing the RABF cycle using the selected one of the available plurality of predefined tape speeds.

9. The system of claim 8, wherein the controller is further adapted for, previous to the calculating the average overhead, detecting a pattern of synchronizing events for writing transactions to the magnetic tape, the detecting triggering a RABF mode of operation.

10. The system of claim 9, wherein the controller is further adapted for, pursuant to performing the RABF cycle:

accessing at least one work copy wrap of the magnetic tape with at least one read/write head of the magnetic tape drive,

writing at least one stored synchronized transaction of the detected pattern from the at least one buffer to the at least one work copy wrap of the magnetic tape,

upon writing the at least one stored synchronized transaction from the at least one buffer to the magnetic tape, accumulating the at least one stored synchronized transaction in the at least one buffer, and

subsequently accessing at least one normal wrap of the magnetic tape separate from the at least one work copy wrap, and recursively writing the at least one accumulated transaction from the at least one buffer to the magnetic tape in a sequence.

11. The system of claim 10, wherein the controller is further adapted for, if the detecting triggers a first occurrence of the RABF mode of operation in a period of time, performing a first RABF cycle using a fastest tape speed of the available plurality of predefined tape speeds.

12. The system of claim 8, wherein the controller is further adapted for, previous to calculating the average overhead, determining if a host transfer rate is smaller than a first tape speed of the available plurality of predefined tape speeds.

13. The system of claim 12, wherein the controller is further adapted for, if the host transfer rate is smaller than the first tape speed, performing the calculating the average overhead for the first tape speed.

14. The system of claim 13, wherein the controller is further adapted for, if an additional tape speed of the available plurality of predefined tape speeds is slower than the first tape speed, determining if the host transfer rate is smaller than the additional tape speed, further wherein if the host transfer rate is smaller, performing the calculating the average overhead for the additional tape speed.

15. A computer program product for writing received synchronized data to magnetic tape having a plurality of wraps using a magnetic tape drive adapted for performing the writing according to an available plurality of predefined tape speeds, the computer program product comprising a computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:

a first executable portion for, for each of the available plurality of predefined tape speeds, calculating an average overhead per synchronized command for performing a recursively accumulated backhitchless flush (RABF) cycle;

a second executable portion for selecting one of the available plurality of predefined tape speeds having a lowest calculated average overhead; and

a third executable portion for performing the RABF cycle using the selected one of the available plurality of predefined tape speeds.

16. The computer program product of claim 15, further including a fourth executable portion for, previous to the calculating the average overhead, detecting a pattern of synchronizing events for writing transactions to the magnetic tape, the detecting triggering a RABF mode of operation.

17. The computer program product of claim 16, further including a fifth executable portion for, pursuant to performing the RABF cycle:

accessing at least one work copy wrap of the magnetic tape with at least one read/write head of the magnetic tape drive,

writing at least one stored synchronized transaction of the detected pattern from a buffer to the at least one work copy wrap of the magnetic tape,

upon writing the at least one stored synchronized transaction from the buffer to the magnetic tape, accumulating the at least one stored synchronized transaction in the buffer, and

subsequently accessing at least one normal wrap of the magnetic tape separate from the at least one work copy wrap, and recursively writing the accumulated transactions from the buffer to the magnetic tape in a sequence.

18. The computer program product of claim 17, further including a sixth executable portion for, if the detecting triggers a first occurrence of the RABF mode of operation in a period of time, performing a first RABF cycle using a fastest tape speed of the available plurality of predefined tape speeds.

19. The computer program product of claim 15, further including a fourth executable portion for, previous to calculating the average overhead, determining if a host transfer rate is smaller than a first tape speed of the available plurality of predefined tape speeds, wherein if the host transfer rate is smaller than the first tape speed, performing the calculating the average overhead for the first tape speed.

20. The computer program product of claim 19, further including a fifth executable portion for, if an additional tape speed of the available plurality of predefined tape speeds is slower than the first tape speed, determining if the host transfer rate is smaller than the additional tape speed, wherein if the host transfer rate is smaller, performing the calculating the average overhead for the additional tape speed.