Storage system with disk drive power-on-reset detection
A disk array controller reliably detects disk drive power-on-reset events that may cause a disk drive that has uncommitted write data stored in its cache to lose such data. The methods for detecting the power-on-reset events include operating the disk drives in an ATA security mode in which a power-on-reset of a disk drive will cause the drive to enter a locked state in which data transfer commands are aborted; and tracking power cycle count attributes of the disk drives over time. When a disk drive power-on-reset event is detected, the disk array may be efficiently restored to an operational state by re-executing or “replaying” a set of write commands that are cached within the disk array controller. The invention is also applicable to single-disk-drive storage systems.
1. A method of detecting disk drive power-on-reset events, comprising:
reading from a disk drive an initial power cycle count attribute of the disk drive, and storing the initial power cycle count attribute in memory;
detecting an event which indicates that the disk drive may have undergone a power-on-reset event; and
in response to detecting the event, reading a current power cycle count attribute of the disk drive, and comparing the current power cycle count attribute to the initial power cycle count attribute to evaluate whether the detected event was caused by a power-on-reset event.
2. The method of claim 1 , wherein the detected event is an event in which the disk drive aborts a command after having been placed in an unlocked state.
3. The method of claim 1 , wherein the detected event is an event in which the disk drive aborts a command as a result of being in a locked ATA security state.
4. The method of claim 1 , wherein the detected event is a disk drive command timeout event.
5. The method of claim 1 , wherein the detected event is an event in which an unexpected disk drive status is detected.
6. The method of claim 1 , further comprising, in response to determining from said comparison that a power-on-reset event occurred, resending write data to the disk drive to correct for a potential loss of write data that was stored in a disk drive's cache but not yet committed to disk media at the time of the power-on-reset event.
7. A disk array system, comprising:
a plurality of disk drives, wherein each disk drive maintains a readable count attribute that is incremented with each power cycle of the disk drive; and
an array controller that controls the plurality of disk drives to implement a disk array;
wherein the array controller is configured to read values of said count attribute from each of the disk drives, to store said count attribute values, and to compare current count attribute values to past count attribute values read from the disk drives to detect unexpected disk drive power-on-reset events.
8. The disk array system of claim 7 , wherein the array controller is configured to compare a disk drive's current count attribute value to a past count attribute value of the disk drive in response to detecting an event which indicates that the disk drive may have undergone a power-on-reset event.
9. The disk array system of claim 8 , wherein the detected event is an event in which the disk drive aborts a command after having been placed in an unlocked state.
10. The disk array system of claim 8 , wherein the detected event is an event in which the disk drive aborts a command as a result of being in a locked ATA security state.
11. The disk array system of claim 8 , wherein the detected event is a disk drive command timeout event.
12. The disk array system of claim 8 , wherein the detected event is an event in which an unexpected disk drive status is detected.
13. The disk array system of claim 7 , wherein the array controller is configured to respond to detecting an unexpected disk drive power-on-reset by resending write commands to the corresponding disk drive to correct for a potential loss of write data.
14. The disk array system of claim 7 , wherein the count attribute is a SMART power cycle count attribute.
15. The disk array system of claim 7 , wherein the disk drives are ATA disk drives.