Recovery from errors in a redundant array of disk drives
First Claim
1. In a machine-effected method of rebuilding data in a redundant array of a plurality of disk drives which includes an error affected disk drive, including the machine-executed steps of:
- detecting and indicating that a one of the disk drives is error affected;
measuring and indicating a rate of machine operations of the array;
establishing a rate of rebuilding data affected by the error affected disk drive which rate is predetermined inversely proportional to said measured and indicated rate of accesses;
intermediate predetermined ones of said accesses which is in said inverse proportion, rebuilding data in a predetermined one of the disk drives for replacing data in error.
1 Assignment
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Accused Products
Abstract
Fault tolerance in a redundant array of disk drives is degraded when error conditions exist in the array. Several methods for rebuilding data of the array to remove the degradation are described. Data rebuilding for entire disk drives and partial data rebuilds of disk drives are described. All rebuild methods tend to reduce the negative affect of using array resources for the data rebuild. In one method rebuilding occurs during idle time of the array. In a second method rebuilding is interleaved between current data area accessing operations of the array at a rate which is inversely proportional to activity level of the array. In a third method, the data are rebuilt when a data area being accessed is a data area needing rebuilding.
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Citations
16 Claims
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1. In a machine-effected method of rebuilding data in a redundant array of a plurality of disk drives which includes an error affected disk drive, including the machine-executed steps of:
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detecting and indicating that a one of the disk drives is error affected; measuring and indicating a rate of machine operations of the array; establishing a rate of rebuilding data affected by the error affected disk drive which rate is predetermined inversely proportional to said measured and indicated rate of accesses; intermediate predetermined ones of said accesses which is in said inverse proportion, rebuilding data in a predetermined one of the disk drives for replacing data in error. - View Dependent Claims (2, 3)
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4. In a machine-effected method of automatically maintaining fault tolerance in a parity array of disk drives including the machine-executed steps of:
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detecting and indicating a degradation of the fault tolerance of the parity array; evaluating and indicating the current information handling activity of the parity array; establishing a plurality of data rebuild methods for the parity array for removing the fault tolerance degradation from the parity array; and analyzing the indicated current information handling activity of the parity array and selecting a one of the plurality of rebuild methods which effects a data rebuild without degrading performance of said current information handling activity more than a predetermined degradation level. - View Dependent Claims (5, 6, 7, 8)
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9. In a machine-effected method of automatically maintaining fault tolerance in a fault tolerant parity array of disk drives including the machine-executed steps of:
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detecting that the parity array is idle; detecting that the parity array fault tolerance is degraded and needs data rebuilding; identifying data rebuild needs; and rebuilding the data at the identified rebuild needs during said detected idle times.
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10. In a machine-effected method of automatically maintaining fault tolerance in a fault tolerant parity array of disk drives including the machine-executed steps of:
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indicating that fault tolerance of the parity array is degraded by a plurality of error-affected addressable data units of the parity array which respectively need data rebuilding to reestablish the fault tolerance; performing a data area access operation to an addressable data unit in the parity array; while performing the data area access operation, detecting and indicating that the data access operation is accessing a one of the error-affected addressable data units needing a data rebuild; and rebuilding the addressable data unit being accessed.
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11. Apparatus having a redundant array of disk devices, the improvement including, in combination:
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rebuild need evaluation means for detecting and indicating a degradation in the redundant array including indicating a one of the disk drives needs to have data rebuilt to such one disk drive; access rate means for measuring and indicating a rate of machine operations of said array; rebuild rate means coupled to said evaluation means and to said access rate means for responding to said indicated rebuild need and to said indicated operations rate for establishing and indicating a predetermined rate of rebuilding for the array for recovering from said degradation of fault tolerance; and rebuild means having a plurality of data rebuild effecting means and being coupled to said rebuild rate means and to said rebuild need means for effecting data rebuild in said one disk drive using a predetermined one of said plurality of data rebuild effecting means. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification