Patent ID: 8230131

Claim:
A method for migrating data of a data storage system comprising data storage having higher speed and comprising other data storage, the method comprising the steps of: identifying at least one group of said data having had at least one indicated I/O activity in each of a plurality of intervals of time, occurring over a string of multiple intervals of time, said I/O activity with respect to the data storage from which data is to be migrated, ignoring said I/O activity exceeding said one indicated I/O activity, wherein the time for each of said multiple intervals selected such that bursts of said I/O activity are likely to be contained in one interval; monitoring said indicated I/O activity separately for each said group of data, and monitoring for the occurrence of I/O activity in an interval; wherein said identifying step comprises identifying groups of data having said I/O activity over a string having a limited group of said intervals; and comprises identifying said I/O activity where I/O activity in some said intervals may be inactive, employing a moving average of said one indicated I/O activity and inactivity of said intervals; wherein said moving average is weighted with greater weight to more recent said I/O activity, said moving average comprises an exponential weighting, and comprises: P =(1 −W )* P _last+ W*S , where: P=present value of exponentially weighted moving average; P_last=last preceding value of P; W=weighting of each interval; and S=1 if I/O activity occurred within interval, 0 if no I/O activity; and classifying said identified at least one group of data to said higher speed data storage.