Preferential caching of uncopied logical volumes in a peer-to-peer virtual tape server
First Claim
1. A method for maintaining data in two storage devices, wherein the data is comprised of a plurality of data sets, comprising:
- maintaining in a first storage device a flag for each data set indicating whether the data set has been copied to a second storage device;
maintaining a timestamp for each data set;
flagging each data set as an uncopied data set when the data set is modified or newly created;
modifying the timestamp for the uncopied data set by adding a period of time; and
removing data from the first storage device based on the timestamp of each data set.
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Accused Products
Abstract
Disclosed is a system, method, and an article of manufacture for preferentially keeping an uncopied data set in one of two storage devices in a peer-to-peer environment when data needs to be removed from the storage devices. Each time a data set is modified or newly created, flags are used to denote whether the data set needs to be copied from one storage device to the other. The preferred embodiments modify the timestamp for each uncopied data set by adding a period of time, and thus give preference to the uncopied data set when the data from the storage device is removed based on the least recently used as denoted by timestamp of each data set. Once the data set is copied, the timestamp is set back to normal by subtracting the same period of time added on when the data set was flagged as needing to be copied.
106 Citations
31 Claims
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1. A method for maintaining data in two storage devices, wherein the data is comprised of a plurality of data sets, comprising:
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maintaining in a first storage device a flag for each data set indicating whether the data set has been copied to a second storage device;
maintaining a timestamp for each data set;
flagging each data set as an uncopied data set when the data set is modified or newly created;
modifying the timestamp for the uncopied data set by adding a period of time; and
removing data from the first storage device based on the timestamp of each data set. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for maintaining data in two storage devices, wherein the data is comprised of a plurality of data sets, comprising:
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means for maintaining in a first storage device a flag for each data set indicating whether the data set has been copied to a second storage device;
means for maintaining a timestamp for each data set;
means for flagging each data set as an uncopied data set when the data set is modified or newly created;
means for modifying the timestamp for the uncopied data set by adding a period of time; and
means for removing data from the first storage device based on the timestamp of each data set. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An article of manufacture containing code for maintaining data in two storage devices, wherein the data is comprised of a plurality of data sets, comprising a computer usable media including at least one computer program embedded therein that is capable or causing at least one computer to perform:
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maintaining in a first storage device a flag for each data set indicating whether the data set has been copied to a second storage device;
maintaining a timestamp for each data set;
flagging each data set as an uncopied data set when the data set is modified or newly created;
modifying the timestamp for the uncopied data set by adding a period of time; and
removing data from the first storage device based on the timestamp of each data set. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification