Method and apparatus for increasing raid write performance by maintaining a full track write counter

Abstract

A method and apparatus for improving write performance in a disk array, wherein unnecessary track grouping is avoided during writes, by using a full track write counter. When a write request is received, the full track write counter for tracks in a stripe of tracks associated with the write request is analyzed to determine whether the write request involves a full track write. A cache destage is subsequently executed based on the analysis. When the write to cache is a full track write, a previous track full track count is fetched from a previous track's full write counter, a full track count of the tracks associated with the write request are set to be equal to the minimum of either the stripe width or the previous track's full track count plus one. When the full track write counter of the last track in the stripe is equal to the stripe width, each track in the stripe is processed for destage, new parity for the stripe is generated based on modifications to each track and new data resulting from the modifications and the new parity are written to a rank.