Data storage device compensating for head/tape wear
A data storage device is disclosed comprising at least one head configured to access a magnetic tape. A plurality of access commands are stored in a command queue, and a wear value is generated for each access command in the command queue, wherein the wear value represents a level of wear on the head or magnetic tape associated with executing the access command. An execution order for the access commands is generated based on the wear values, and at least one of the access commands is executed based on the execution order.
1. A data storage device configured to access a magnetic tape, the data storage device comprising:
at least one head configured to access the magnetic tape; and
control circuitry configured to:
store a plurality of access commands in a command queue;
generate a wear value for each access command in the command queue, wherein the wear value represents a level of wear on the head or magnetic tape associated with executing the access command;
generate an execution order for the access commands based on the wear values; and
execute at least one of the access commands based on the execution order.
2. The data storage device as recited in claim 1 , wherein the data storage device comprises the magnetic tape.
3. The data storage device as recited in claim 1 , wherein:
the magnetic tape is housed in a cartridge assembly; and
the data storage device comprises a tape drive assembly configured to receive the cartridge assembly.
4. The data storage device as recited in claim 1 , wherein the wear value comprises a longitudinal distance of the magnetic tape for the head to reach a segment of the magnetic tape in order to execute the access command.
5. The data storage device as recited in claim 1 , wherein the wear value comprises a lateral distance of the magnetic tape for the head to seek to a data track of the magnetic tape in order to execute the access command.
6. The data storage device as recited in claim 1 , wherein the wear value comprises a turnaround direction of the magnetic tape in order to execute the access command.
7. The data storage device as recited in claim 1 , wherein the wear value is generated by weighting a plurality of factors including at least:
a longitudinal distance of the magnetic tape for the head to reach a segment of the magnetic tape in order to execute the access command;
a lateral distance of the magnetic tape for the head to seek to a data track of the magnetic tape in order to execute the access command; and
a turnaround direction of the magnetic tape in order to execute the access command.
8. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
generate an access latency for each access command in the command queue, wherein the access latency includes an access time for the head to reach a segment of the magnetic tape in order to execute the access command; and
generate the execution order based on the wear values and the access latencies.
9. The data storage device as recited in claim 8 , wherein the control circuitry is further configured to:
maintain an overall wear measurement;
weight the wear values based on the overall wear measurement; and
generate the execution order based on the weighted wear values and the access latencies.
10. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
maintain an accumulated wear measurement for each of a plurality of segments of the magnetic tape;
weight the wear values based on the accumulated wear measurements; and
generate the execution order based on the weighted wear values.
11. The data storage device as recited in claim 10 , wherein the control circuitry is further configured to generate the execution order so as to spread out the wear of the magnetic tape across the plurality of segments.
12. The data storage device as recited in claim 10 , wherein each segment consists of an error correction code (ECC) codeword.
13. A data storage device configured to access a magnetic tape, the data storage device comprising:
at least one head configured to access the magnetic tape; and
control circuitry configured to:
maintain an accumulated wear measurement for each of a plurality of segments of the magnetic tape; and
seek the head laterally over the magnetic tape based on the accumulated wear measurements.
14. The data storage device as recited in claim 13 , wherein the data storage device comprises the magnetic tape.
15. The data storage device as recited in claim 13 , wherein:
the magnetic tape is housed in a cartridge assembly; and
the data storage device comprises a tape drive assembly configured to receive the cartridge assembly.
16. The data storage device as recited in claim 13 , wherein the control circuitry is further configured to seek the head laterally over the magnetic tape in order to spread out wear of the magnetic tape across the plurality of segments.
17. The data storage device as recited in claim 16 , wherein each segment consists of an error correction code (ECC) codeword.
18. The data storage device as recited in claim 13 , wherein the control circuitry is further configured to delay the seek in order to prevent the head from passing over one of the segments based on the accumulated wear measurement for the segment.
19. The data storage device as recited in claim 13 , wherein the control circuitry is further configured to step seek the head laterally over the magnetic tape based on the accumulated wear measurements.
20. The data storage device as recited in claim 13 , wherein the control circuitry is further configured to serpentine seek the head laterally over the magnetic tape based on the accumulated wear measurements.
21. The data storage device as recited in claim 13 , wherein the control circuitry is further configured to reverse a direction of the head prior to seeking the head laterally over the magnetic tape based on the accumulated wear measurements.
22. A data storage device configured to access a magnetic tape, the data storage device comprising:
at least one head configured to access the magnetic tape; and
a means for generating a wear value for each of a plurality of access command in a command queue, wherein the wear value represents a level of wear on the magnetic tape associated with executing the access command; and
a means for executing the access commands based on an execution order determined based on the wear values.
23. The data storage device as recited in claim 22 , further comprising a means for maintaining an accumulated wear measurement for each of a plurality of segments of the magnetic tape.
24. The data storage device as recited in claim 23 , wherein the execution order is determined based on the wear values and the accumulated wear measurements.
25. A data storage device configured to access a magnetic tape, the data storage device comprising:
at least one head configured to access the magnetic tape; and
control circuitry configured to:
define at least one longitudinal reserved band on the magnetic tape, wherein data is not recorded in the longitudinal reserved band;
receive an access command to access a longitudinal data band on the magnetic tape; and
scan the head along the longitudinal reserved band and then scan the head along the longitudinal data band in order to execute the access command.
26. A data storage device configured to access a magnetic tape, the data storage device comprising:
at least one head configured to access the magnetic tape; and
control circuitry configured to:
define at least one lateral reserved band on the magnetic tape, wherein data is not recorded in the lateral reserved band;
receive an access command to access a longitudinal data band on the magnetic tape; and
seek the head along the lateral reserved band and then scan the head along the longitudinal data band in order to execute the access command.