Patent ID: 7039657
Filing Date: 2006-05-02
Classification: G06F,Y10S

Abstract:
1. A method for accessing a plurality of data sets from one of a first, second, third and fourth storage devices, including a copy of the data set, comprising: maintaining a flag for each of the first and second storage devices indicating whether a previous access attempt of the data set from the first and second storage devices failed; maintaining a data level for each of the plurality of data sets in each of the first and second storage devices indicating a number of times the data set has been updated, wherein there is a separate data level for each copy of one data set in the first and second storage devices and wherein the data levels for the first and second storage devices having copies of one data set are capable of being equal; receiving a request to one data set; accessing the data set from one of the third and fourth storage devices if the data set is in one of the third and fourth storage devices; selecting the first or second storage device having a higher data level for the requested data set if the data levels are not equal and if the data set is not in one of the third and fourth storage devices; selecting the first or second storage device having the flag indicating that no previous access attempt failed if the flag for the other of the first or second storage device indicates that one previous access attempt of the data set from the first or second storage device failed and if the data levels are equal and if the data set is not in one of the third and fourth storage devices; accessing the data set from the selected first or second storage device; copying the data set from the first storage device to the third storage device when accessing the data set from the first storage device; and copying the data set from the second storage device to the fourth storage device when accessing the data set from the first storage device.