Patent ID: 8370597
Filing Date: 2013-02-05
Classification: G06F

Abstract:
1. A method for migrating data between tiers of a storage system, when the method is executed by a computer system, the method comprising: subdividing a storage capacity of the storage system into a set of territories; partitioning the set of territories into tiers; imposing an ordering on the tiers; maintaining an information lifecycle management metric for each territory; promoting a territory that is more eligible into a highest possible tier in response to storage capacity being available in a higher tier; demoting a territory that is less eligible into a lower tier in response to a more eligible territory existing in the lower tier and no storage capacity being available for promotion of the more eligible territory; and demoting a least eligible territory to a next lowest tier in response to a less eligible territory existing in the next highest tier and no storage capacity being available for demotion of the less eligible territory, wherein maintaining an information lifecycle management metric comprises combining an age statistic and a frequency statistic into a single metric, wherein the information lifecycle management metric is updated once per update period, wherein each update period has a consistent amount of time, and wherein a sign bit of the single metric is set or cleared in response to the single metric storing the frequency statistic and the age statistic.