Maintaining data integrity in data migration operations using per-migration device error flags
First Claim
1. A method of managing state transitions in a data migration operation, the migration operation including an initial setup state, a set of write cloning states in which a target storage device is becoming or is maintained synchronized with a source storage device, and a later committed state in which the target storage device is used to the exclusion of the source storage device, the set of write cloning states spanning a system shutdown/startup cycle, comprising:
- upon entering the write cloning states, setting an error flag used to protect against data corruption in the event of a non-clean system shutdown;
during the write cloning states, performing only allowed state transitions based on recorded device faults, the allowed state transitions including a non-error transition to the committed state when no device fault is recorded for the target storage device and an error transition to the setup state when a device fault is recorded for the target storage device;
in the event of a clean system shutdown, completing a shutdown procedure in which a device fault detected during writing to the target storage device is recorded and the error flag is cleared, the recording of the device fault forcing the error transition of the migration operation during subsequent operation after system startup; and
during the system startup prior to enabling application input/output to the target storage device, determining whether the error flag is set indicating that the shutdown procedure was not completed, and only if the error flag is set then recording a device fault for the target storage device to force the error transition of the migration operation during subsequent operation.
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Accused Products
Abstract
A data migration operation uses an error flag to protect against data corruption. During write cloning states, the error flag is set and only allowed state transitions are performed, including a non-error transition to a committed state when no device fault is recorded for a target storage device and an error transition to a setup state when a device fault is recorded for the target storage device. In a clean system shutdown, a shutdown procedure records a detected target storage device fault and clears the error flag; the recorded device fault later forces the error transition of the migration operation. During the system startup, if the error flag is set then a target storage device fault is recorded to likewise later force the error transition of the migration operation, on the assumption that a detected fault may exist but be unrecorded because the shutdown procedure did not complete during shutdown.
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Citations
18 Claims
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1. A method of managing state transitions in a data migration operation, the migration operation including an initial setup state, a set of write cloning states in which a target storage device is becoming or is maintained synchronized with a source storage device, and a later committed state in which the target storage device is used to the exclusion of the source storage device, the set of write cloning states spanning a system shutdown/startup cycle, comprising:
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upon entering the write cloning states, setting an error flag used to protect against data corruption in the event of a non-clean system shutdown; during the write cloning states, performing only allowed state transitions based on recorded device faults, the allowed state transitions including a non-error transition to the committed state when no device fault is recorded for the target storage device and an error transition to the setup state when a device fault is recorded for the target storage device; in the event of a clean system shutdown, completing a shutdown procedure in which a device fault detected during writing to the target storage device is recorded and the error flag is cleared, the recording of the device fault forcing the error transition of the migration operation during subsequent operation after system startup; and during the system startup prior to enabling application input/output to the target storage device, determining whether the error flag is set indicating that the shutdown procedure was not completed, and only if the error flag is set then recording a device fault for the target storage device to force the error transition of the migration operation during subsequent operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A non-transitory computer readable medium having computer program instructions recorded thereon, the computer program instructions being executable by a computer to cause the computer to perform a method of managing state transitions in a data migration operation, the migration operation including an initial setup state, a set of write cloning states in which a target storage device is becoming or is maintained synchronized with a source storage device, and a later committed state in which the target storage device is used to the exclusion of the source storage device, the set of write cloning states spanning a system shutdown/startup cycle, the method including:
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upon entering the write cloning states, setting an error flag used to protect against data corruption in the event of a non-clean system shutdown; during the write cloning states, performing only allowed state transitions based on recorded device faults, the allowed state transitions including a non-error transition to the committed state when no device fault is recorded for the target storage device and an error transition to the setup state when a device fault is recorded for the target storage device; in the event of a clean system shutdown, completing a shutdown procedure in which a device fault detected during writing to the target storage device is recorded and the error flag is cleared, the recording of the device fault forcing the error transition of the migration operation during subsequent operation; and during the system startup prior to enabling application input/output to the target storage device, determining whether the error flag is set indicating that the shutdown procedure was not completed, and only if the error flag is set then recording a device fault for the target storage device to force the error transition of the migration operation during subsequent operation. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification