Patent ID: 7908408

Claim:
A storage device which virtualizes one or a plurality of logical volumes which an external storage device connected to the storage device offers respectively and offers virtualized logical volumes to a host computer, wherein the storage device includes: a plurality of ports which are connected to the external storage device via respectively different paths; and a channel processor which generates a command corresponding to a read request or a write request given from the host computer, and issues the generated command to the external storage device, and the channel processor is configured, for every kind of the command, to issue a test command corresponding to the generated commands to the external storage device by using each of a plurality of command issuing methods and to measure an I/O performance to process the test command by using each of said plurality of command issuing methods, and to set a command issuing method selected from said plurality of command issuing methods to issue the generated command to the external storage device in an operation time based on the result of measurement of the I/O performance processing the test command using each of the command issuing method.