Method, system and article of manufacture for recovery from a failure in a cascading PPRC system
First Claim
1. A method of recovery from a data storage system failure in a data storage system having a host computer writing data to a first storage unit associated with a first storage controller synchronously mirroring the data to a second storage unit associated with a second storage controller asynchronously mirroring the data to a third storage unit, the method comprising:
- detecting a failure associated with the first storage unit;
writing data updates directly to the second storage unit;
correcting the failure associated with the first storage unit; and
synchronously mirroring the data updates from the second storage unit to the first storage unit.
1 Assignment
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Accused Products
Abstract
A method of recovery from a data storage system failure in a data storage system having a host computer writing data to a first storage unit with a first storage controller synchronously mirroring the data to a second storage unit, and with a second storage controller asynchronously mirroring the data to a third storage unit. The method begins with the detection of a failure associated with the first storage unit. Upon detection of the error or failure associated with the first storage unit, the synchronous data mirroring relationship between the first storage unit and the second storage unit is terminated and the host is directed to write data updates directly to the second storage unit. Upon correction of the failure associated with the first storage unit, the asynchronous mirroring of data updates from the second storage unit to the third storage unit is suspended and synchronous mirroring of the data updates in a reverse direction, from the second storage unit to the first storage unit, is commenced. When a full duplex state is reached between the first storage unit and the second storage unit, the synchronous PPRC relationship with the first storage volume mirroring data to the second storage volume may be reestablished and host I/O writes to the first storage unit may be resumed.
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Citations
30 Claims
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1. A method of recovery from a data storage system failure in a data storage system having a host computer writing data to a first storage unit associated with a first storage controller synchronously mirroring the data to a second storage unit associated with a second storage controller asynchronously mirroring the data to a third storage unit, the method comprising:
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detecting a failure associated with the first storage unit;
writing data updates directly to the second storage unit;
correcting the failure associated with the first storage unit; and
synchronously mirroring the data updates from the second storage unit to the first storage unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system for copying stored data and having the ability to recover from a failure, comprising:
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a second storage controller associated with a second storage unit, the second storage controller synchronously receiving mirrored data from a first storage controller associated with a host computer and a first storage unit, the second storage controller further asynchronously mirroring the data to a third storage controller associated with a third storage unit;
means for detecting a failure associated with the first storage unit;
means for writing data updates from the host computer to the second storage controller upon detection of the failure associated with the first storage unit;
means for synchronously mirroring the data updates from the second storage unit to the first storage unit upon correction of the failure associated with the first storage unit. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. An article of manufacture for use in programming a data storage system to recover from a failure, the data storage system having a host computer writing data to a first storage unit associated with a first storage controller synchronously mirroring the data to a second storage unit associated with a second storage controller asynchronously mirroring the data to a third storage unit, the article of manufacture comprising a storage medium having logic embedded therein to cause components of the data storage system to:
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detect a failure associated with the first storage unit;
write data updates directly to the second storage unit;
correct the failure associated with the first storage unit; and
synchronously mirror the data updates from the second storage unit to the first storage unit. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification