TRIPLE PARITY TECHNIQUE FOR ENABLING EFFICIENT RECOVERY FROM TRIPLE FAILURES IN A STORAGE ARRAY
First Claim
1. A method for recovering from three failed data storage devices, comprising:
- establishing a plurality of storage devices to hold data, referred to as the data storage devices;
establishing a storage device to hold row parity for the data devices, referred to as the row parity storage device, and referring to the data storage devices and the row parity storage device together as a set of storage devices;
establishing a diagonal parity storage device to hold diagonal parity computed over the set of storage devices;
establishing an anti-diagonal parity storage device to hold anti-diagonal parity computed over the set of storage devices;
in the event of a failure of three data storage devices of the set of storage devices, choosing a first failed storage device to restore;
computing a missing block of the first failed storage device using remaining storage devices of the set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device; and
using diagonal parity restoration techniques to restore the remaining two failed storage devices.
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Abstract
A method for recovering from three failed data storage devices is disclosed. A plurality of data storage devices hold data, and a row parity storage device holds row parity for them. The data storage devices and the row parity storage device form a set of storage devices. A diagonal parity storage device and an anti-diagonal parity storage device hold parity computed diagonally over the set of storage devices. In the event of a failure of three data storage devices of the set of storage devices, a first failed storage device is chosen for first restoration. A missing block of the first failed storage device is computed by using the remaining set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device. The remaining two failed storage devices are restored by a diagonal parity restoration technique.
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Citations
22 Claims
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1. A method for recovering from three failed data storage devices, comprising:
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establishing a plurality of storage devices to hold data, referred to as the data storage devices; establishing a storage device to hold row parity for the data devices, referred to as the row parity storage device, and referring to the data storage devices and the row parity storage device together as a set of storage devices; establishing a diagonal parity storage device to hold diagonal parity computed over the set of storage devices; establishing an anti-diagonal parity storage device to hold anti-diagonal parity computed over the set of storage devices; in the event of a failure of three data storage devices of the set of storage devices, choosing a first failed storage device to restore; computing a missing block of the first failed storage device using remaining storage devices of the set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device; and using diagonal parity restoration techniques to restore the remaining two failed storage devices. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A computer data storage system apparatus, comprising:
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a plurality of storage devices to hold data, referred to as the data storage devices; a storage device to hold row parity for the data storage devices, referred to as the row parity storage device, and referring to the data storage devices and the row parity storage device together as a set of storage devices; a diagonal parity storage device to hold diagonal parity computed over the set of storage devices; an anti-diagonal parity storage device to hold anti-diagonal parity computed over the set of storage devices; in the event of a failure of three data storage devices of the set of storage devices, a processor to choose a first failed storage device to restore; a process executing on the processor to compute a missing block of the first failed storage device by solving for a value of the block using equations generated from the remaining storage devices of the set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device; and the processor to use diagonal parity restoration techniques to restore the remaining two failed storage devices, to recover from three failed data storage devices. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A computer readable storage media, comprising:
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said computer readable storage media containing program instructions for execution on a processor for a method of recovering from three failed data storage devices, the program instructions for, establishing a plurality of storage devices to hold data, referred to as the data storage devices; establishing a storage device to hold row parity for the data devices, referred to as the row parity storage device, and referring to the data storage devices and the row parity storage device together as a set of storage devices; establishing a diagonal parity storage device to hold diagonal parity computed over the set of storage devices; establishing an anti-diagonal parity storage device to hold anti-diagonal parity computed over the set of storage devices; in the event of a failure of three data storage devices of the set of storage devices, choosing a first failed storage device to restore; computing a missing block of the first failed storage device by solving for a value of the block using equations generated from the remaining storage devices of the set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device; and using diagonal parity restoration techniques to restore the remaining two failed storage devices.
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22. A method for recovering from three failed data storage devices in a computer data storage system having a plurality of storage devices to hold data, referred to as the data storage devices, and having a storage device to hold row parity for the data storage devices, referred to as the row parity storage device, and referring to the data storage devices and the row parity storage device together as a set of storage devices, comprising:
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establishing a diagonal parity storage device to hold diagonal parity computed over the set of storage devices; establishing an anti-diagonal parity storage device to hold anti-diagonal parity computed over the set of storage devices; configuring the data storage system to respond to a failure of three storage devices of the set of storage devices by choosing a first failed storage device to restore; configuring the data storage system to compute a missing block of the first failed storage device by using the remaining storage devices of the set of storage devices, and the diagonal parity storage device, and the anti-diagonal parity storage device; and configuring the data storage system to use diagonal parity restoration techniques to restore the remaining two failed storage devices.
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Specification