Patent ID: 8127047

Claim:
A storage system, comprising: a controller connected to a plurality of hosts and which analyzes and processes commands from the plurality of hosts; and a plurality of disk drives forming one or more logical volumes to be accessed by the controller, and wherein, upon receiving commands from the plurality of hosts, the controller analyzes whether the IO processing attached to the received commands is random IO processing or sequential IO processing, and executes extent exclusive wait processing which causes access to the logical volume to enter a wait state or access processing to the logical volume in accordance with the analytical result, wherein, when the controller analyzes that the IO processing attached to the received commands is random IO processing, the controller determines, based on valid extents which are access ranges that are different from the access range designated in each DX command and prescribed in seek parameters within information attached to an LOC command, whether at least a part of each of the valid extents overlaps; the controller executes extent exclusive wait processing which causes access to the logical volume to enter a wait state upon obtaining a positive determination result in this determination; and the controller executes access processing to the logical volume upon obtaining a negative determination result in the determination; and wherein, when the controller analyzes that the IO processing attached to the received commands is sequential IO processing, the controller determines whether a competition ratio occupied by an IO count in which at least a part of the access range designated in each of the DX commands overlaps within the IO count to the same logical volume among the plurality of logical volumes exceeds a first threshold value, and whether an invalid extent ratio occupied by invalid extents showing an access range outside the valid extent among the access ranges designated in each of the DX commands exceeds a second threshold value; the controller determines whether information attached to each of the DX commands is short if the competition ratio exceeds the first threshold value and the invalid extent ratio exceeds the second threshold value; the controller executes processing of waiting to receive all information attached to each of the DX commands upon obtaining a determination result to the effect that the information attached to each of the DX commands is short; and the controller executes the extent exclusive wait processing or the access processing to the logical volume based on the access range designated in each of the DX commands upon obtaining a determination result to the effect that the information attached to each of the DX commands is long.