System and method for handling temporary errors on a redundant array of independent tapes (RAIT)
First Claim
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1. A method for storing data in a storage system having N storage elements arranged in parallel for concurrent access, wherein N is an integer greater than three, wherein N−
- 2 of the N storage elements are designated as data storage elements for each row of data and the remaining two of the N storage elements are designated as first and second redundant information storage elements for each row of data, the method comprising;
determining first redundancy information based on a first row of data to be striped across the N−
2 storage elements;
determining first additional redundancy information based on the first row of data to be striped across the N−
2 storage elements and the determined first redundancy information;
determining which of the N−
2 storage elements are responsive for receiving data;
striping the first row of data across the responsive storage elements of the N−
2 storage elements if at least N−
3 of the N−
2 storage elements are responsive for receiving data;
writing the first redundancy information to the first redundant information storage element;
writing the first additional redundancy information to the second redundant information storage element if all of the N−
2 storage elements are responsive for receiving data; and
writing the data to be received by one of the N−
2 storage elements to the second redundant information storage element if the one of the N−
2 storage elements is unresponsive for receiving data.
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Abstract
A system and method for storing data in a storage system having storage elements arranged in parallel for concurrent access such that data can be continuously communicated to the storage element array while one of the storage elements is in error recovery. Some of the storage elements receive data of a stripe and the remaining storage elements receive parity information based on the data of the stripe. An unresponsive storage element in error recovery is dropped from the other storage elements for receiving data until error recovery is complete and the storage element is responsive for receiving data. While the storage element is unresponsive, one of the storage elements scheduled to receive parity information receives data to be written to the unresponsive storage element instead of the parity information. Communication to the storage elements continues while the failed storage element is in error recovery. Error recovery is accomplished by using the parity information of the other parity information storage elements.
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Citations
6 Claims
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1. A method for storing data in a storage system having N storage elements arranged in parallel for concurrent access, wherein N is an integer greater than three, wherein N−
- 2 of the N storage elements are designated as data storage elements for each row of data and the remaining two of the N storage elements are designated as first and second redundant information storage elements for each row of data, the method comprising;
determining first redundancy information based on a first row of data to be striped across the N−
2 storage elements;
determining first additional redundancy information based on the first row of data to be striped across the N−
2 storage elements and the determined first redundancy information;
determining which of the N−
2 storage elements are responsive for receiving data;
striping the first row of data across the responsive storage elements of the N−
2 storage elements if at least N−
3 of the N−
2 storage elements are responsive for receiving data;
writing the first redundancy information to the first redundant information storage element;
writing the first additional redundancy information to the second redundant information storage element if all of the N−
2 storage elements are responsive for receiving data; and
writing the data to be received by one of the N−
2 storage elements to the second redundant information storage element if the one of the N−
2 storage elements is unresponsive for receiving data.- View Dependent Claims (2, 3)
the storage elements are magnetic tape drives.
- 2 of the N storage elements are designated as data storage elements for each row of data and the remaining two of the N storage elements are designated as first and second redundant information storage elements for each row of data, the method comprising;
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3. The method of claim 1 wherein:
the storage elements are magnetic disk drives.
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4. A data storage system comprising:
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N storage elements arranged in parallel for concurrent access, wherein N is an integer greater than three, wherein N−
2 of the N storage elements are designated as data storage elements for each row of data and the remaining two of the N storage elements are designated as first and second redundant information storage elements for each row of data; and
a controller connected to each of the N storage elements, the controller operable for determining first redundancy information based on a first row of data to be striped across the N−
2 storage elements, determining first additional redundancy information based on the determined first redundancy information and the first row of data to be striped across the N−
2 storage elements, determining which of the N−
2 storage elements are responsive for receiving data, striping the first row of data across the responsive storage elements of the N−
2 storage elements if at least N−
3 of the N−
2 storage elements are responsive for receiving data, writing the first redundancy information to the first redundant information storage element, writing the first additional redundancy information to the second redundant information storage element if all of the N−
2 storage elements are responsive for receiving data, and writing the data to be received by one of the N−
2 storage elements to the second redundant information storage element if the one of the N−
2 storage elements is unresponsive for receiving data.- View Dependent Claims (5, 6)
the storage elements are magnetic tape drives.
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6. The system of claim 4 wherein:
the storage elements are magnetic disk drives.
Specification
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Current AssigneeOracle America, Inc. (Oracle Corporation)
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Original AssigneeStorage Technology Corp (Oracle Corporation)
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InventorsHughes, James P.
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Primary Examiner(s)BADERMAN, SCOTT T
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Application NumberUS09/400,652Time in Patent Office1,267 DaysField of Search714/6, 714/7, 714/8, 714/770, 711/114US Class Current714/6.21CPC Class CodesG06F 11/1084 Degraded mode, e.g. caused ...G06F 2211/108 RAIT, i.e. RAID on tape drive
