Disk drive steering write data to write cache based on workload
View Patent ↗A disk drive is disclosed comprising a non-volatile write cache and a head actuated over a disk. A plurality of write commands are received from a host, wherein each write command comprises write data. A workload for a non-cache area of the disk is determined, and when the workload for the non-cache area of the disk is less than a threshold independent of a workload for the write cache, substantially all of the write data is stored in the non-cache area of the disk. When the workload for the non-cache area of the disk is greater than the threshold independent of the workload for the write cache, a first percentage of the write data is stored in the non-volatile write cache and a second percentage of the write data is stored in the non-cache area of the disk, wherein the first percentage is proportional to the workload for the non-cache area of the disk.
1. A disk drive comprising:
a non-volatile write cache;
a disk;
a head actuated over the disk; and
control circuitry operable to:
receive a plurality of write commands from a host, wherein each write command comprises write data;
determine a workload for a non-cache area of the disk independent of a sequentiality of the write commands;
when the workload for the non-cache area of the disk is less than a threshold independent of a workload for the write cache, store substantially all of the write data in the non-cache area of the disk; and
when the workload for the non-cache area of the disk is greater than the threshold independent of the workload for the write cache, store a first percentage of the write data in the non-volatile write cache and a second percentage of the write data in the non-cache area of the disk, wherein the first percentage is proportional to the workload for the non-cache area of the disk.
2. The disk drive as recited in claim 1 , wherein the non-volatile write cache comprises a non-volatile semiconductor memory.
3. The disk drive as recited in claim 1 , wherein the non-volatile write cache comprises part of the disk.
4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
store the plurality of write commands in a command queue; and
determine the workload for the non-cache area of the disk based on a number of commands stored in the command queue.
5. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to determine the workload based on a frequency of the write commands received from the host.
6. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
store the plurality of write commands in a disk command queue; and
determine the workload based on a rotational position optimization (RPO) algorithm for selecting the write commands from the disk command queue based at least on a radial location of the head.
7. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
maintain a plurality of access patterns of the write commands received from the host; and
determine the workload based on the access patterns.
8. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
receive a command load message from the host; and
determine the workload based on the command load message.
9. The disk drive as recited in claim 1 , wherein the first and second percentages are further based on an amount of free space in the non-volatile write cache.
10. The disk drive as recited in claim 1 , wherein the first and second percentages are further based on a percentage of life remaining for the non-volatile write cache.
11. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to flush the write data from the non-volatile write cache to the non-cache area of the disk during an idle mode.
12. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
execute the write commands based on a rotational position optimization (RPO) algorithm for the disk; and
select the write data to be stored in the non-volatile write cache in response to the RPO algorithm.
13. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to select the write data to be stored in the non-volatile write cache in response to a time-out limit assigned to each write command.
14. A method of operating a disk drive, the disk drive comprising a head actuated over a disk and a non-volatile write cache, the method comprising:
receiving a plurality of write commands from a host, wherein each write command comprises write data;
determining a workload for a non-cache area of the disk independent of a sequentiality of the write commands;
when the workload for the non-cache area of the disk is less than a threshold independent of a workload for the write cache, store substantially all of the write data in the non-cache area of the disk; and
when the workload for the non-cache area of the disk is greater than the threshold independent of the workload for the write cache, storing a first percentage of the write data in the non-volatile write cache and a second percentage of the write data in the non-cache area of the disk, wherein the first percentage is proportional to the workload for the non-cache area of the disk.
15. The method as recited in claim 14 , wherein the non-volatile write cache comprises a non-volatile semiconductor memory.
16. The method as recited in claim 14 , wherein the non-volatile write cache comprises part of the disk.
17. The method as recited in claim 14 , further comprising:
storing the plurality of write commands in a command queue; and
determining the workload for the non-cache area of the disk based on a number of commands stored in the command queue.
18. The method as recited in claim 14 , further comprising determining the workload based on a frequency of the write commands received from the host.
19. The method as recited in claim 14 , further comprising:
storing the plurality of write commands in a disk command queue; and
determining the workload based on a rotational position optimization (RPO) algorithm for selecting the write commands from the disk command queue based at least on a radial location of the head.
20. The method as recited in claim 14 , further comprising:
maintaining a plurality of access patterns of the write commands received from the host; and
determining the workload based on the access patterns.
21. The method as recited in claim 14 , further comprising:
receiving a command load message from the host; and
determining the workload based on the command load message.
22. The method as recited in claim 14 , wherein the first and second percentages are further based on an amount of free space in the non-volatile write cache.
23. The method as recited in claim 14 , wherein the first and second percentages are further based on a percentage of life remaining for the non-volatile write cache.
24. The method as recited in claim 14 , further comprising flushing the write data from the non-volatile write cache to the non-cache area of the disk during an idle mode.
25. The method as recited in claim 14 , further comprising:
executing the write commands based on a rotational position optimization (RPO) algorithm for the disk; and
selecting the write data to be stored in the non-volatile write cache in response to the RPO algorithm.
26. The method as recited in claim 14 , further comprising selecting the write data to be stored in the non-volatile write cache in response to a time-out limit assigned to each write command.