Scheduling low-priority disk seeks for multi-actuator data storage device
A first time period is determined during which a first head driven by a first actuator will be performing a track-following operation. A second time period is also determined during which a second head driven by a second actuator will be performing a low-priority disk access operation that includes a seek. The first and second actuators are independently movable such that the first and second disk access operations are capable of being performed in parallel. If it is determined that the seek of the second head will impact servo control of the track-following operation of the first head, a start time of the seek of the second head is changed to correspond to a time that mitigates impacts to the track-following operation of the first head.
1. A method, comprising:
determining a first time period during which a first head driven by a first actuator will be performing a track-following operation;
determining a second time period during which a second head driven by a second actuator will be performing a low-priority disk access operation that includes a seek, the first and second actuators independently movable such that disk access operations are performed in parallel by the first and second actuators;
determining that the seek of the second head will impact servo control of the track-following operation of the first head; and
in response to the determination that the seek will impact the first head, changing a start time of the seek of the second head to correspond to a time that mitigates impacts to the track-following operation of the first head.
2. The method of claim 1 , wherein the low-priority disk access operation comprises a flush of a write queue associated with the second head.
3. The method of claim 2 , further comprising, if a size of the write queue exceeds a threshold, changing the low-priority disk access operation to a high-priority disk access operation that will be scheduled without regards seeks of the second head impacting operations of the first head.
4. The method of claim 2 , further comprising, if a score of the write queue exceeds a threshold, changing the low-priority disk access operation to a high-priority disk access operation that will be scheduled without regards to seeks of the second head impacting operations of the first head, the score comprising a combination of the length of each pending request in the write queue times a priority of each pending request.
5. The method of claim 1 , wherein the low-priority disk access operation comprises a background operation.
6. The method of claim 1 , further comprising, in response to the determination that the seek will impact the track following operation of the first head, breaking the seek of the second head into multiple seeks with an idle time therebetween, the idle time corresponding to the track-following operation.
7. The method of claim 6 , wherein at least one of the multiple seeks is slowed to fit into a seek safe time period of the first head.
8. The method of claim 1 , wherein the time that mitigates impacts to the track-following operation of the first head comprises a seek time of the first head before or after the track following operation.
9. The method of claim 1 , wherein the time that mitigates impacts to the track-following operation of the first head comprises a time when the first head is track following but not reading or writing to a disk.
10. An apparatus, comprising:
servo control circuitry operable to independently move first and second actuators such that first and second disk access operations are performed in parallel by respective first and second heads of the first and second actuators; and
a system controller coupled to the servo control circuitry and operable to:
determine a first time period during which the first head will be performing a track-following operation;
determine a second time period during which the second head will be performing a low-priority disk access operation that includes a seek;
determine that the seek of the second head will impact servo control of the track-following operation of the first head; and
in response to the determination that the seek will impact the first head, change a start time of the seek of the second head to correspond to a time that mitigates impacts to the track-following operation of the first head.
11. The apparatus of claim 10 , wherein the low-priority disk access operation comprises a flush of a write queue associated with the second head.
12. The apparatus of claim 11 , wherein the system controller is further operable to, if a size of the write queue exceeds a threshold, change the low-priority disk access operation to a high-priority disk access operation that will be scheduled without regards seeks of the second head impacting operations of the first head.
13. The apparatus of claim 11 , wherein the system controller is further operable to, if a score of the write queue exceeds a threshold, changing the low-priority disk access operation to a high-priority disk access operation that will be scheduled without regards seeks of the second head impacting operations of the first head, the score comprising a combination of the length of each pending request in the write queue times a priority of each pending request.
14. The apparatus of claim 10 , wherein the system controller is further operable to, in response to the determination that the seek will impact the first head, breaking the seek of the second head into multiple seeks with an idle time therebetween, the idle time corresponding to the track-following operation.
15. The apparatus of claim 14 , wherein at least one of the multiple seeks is slowed to fit into a seek safe time period of the first head.
16. The apparatus of claim 10 , wherein the time that mitigates impacts to the track-following operation of the first head comprises a seek time of the first head before or after the track following operation.
17. The apparatus of claim 10 , wherein the time that mitigates impacts to the track-following operation of the first head comprises a time when the first head is track following but not reading or writing to a disk.
18. A system comprising:
first and second actuators comprising respective first and second heads, the first and second actuators independently performing first and second disk access operations in parallel over one or more disks; and
a system controller coupled to the first and second actuators and operable to:
determine a first time period during which the first head will be performing a track-following operation;
determine a second time period during which the second head will be performing a low-priority disk access operation that includes a seek;
determine that the seek of the second head will impact servo control of the track-following operation of the first head; and
in response to the determination that the seek will impact the first head, change a start time of the seek of the second head to correspond to a time that mitigates impacts to the track-following operation of the first head.
19. The system of claim 18 , wherein the time that mitigates impacts to the track-following operation of the first head comprises a seek time of the first head before or after the track following operation.
20. The system of claim 18 , wherein the time that mitigates impacts to the track-following operation of the first head a time when the first head is track following but not reading or writing to a disk.