Method and storage controller for determining an access characteristic of a data entity

摘要

Determining a characteristic of a data entity based on a frequency of access to said data entity in a storage system using a counting bloom filter (CBF') comprising a set (S') of counters (C1); and a data structure having a set of elements each corresponding to a counter. To avoid counter overflow the counting bloom filter is operated for an interval in time wherein the set of counters are reset at the start of the interval. Each time said data entity is accessed during the interval a value of at least one counter (C1) to which said data entity is mapped in the counting bloom filter is increased. At the end of the interval the values of the elements in the data structure are updated based on the current value of that element and the value of the counter to which it is assigned. The interval in time may be a predefined number of accesses. A plurality of counting bloom filters can be used. The method may produce a heat map which is used for selectively populating a cache with â hotâ data or controlling data placement of â hotâ data in fastest storage tier of a tiered storage system.