Storage apparatus and data access method

A data access method which employs a storage apparatus which is connected via a network to a host apparatus that requests data I/Os,

• the storage apparatus including:
• a plurality of microprocessors which control data I/O to and from a plurality of storage devices on the basis of the data I/O requests from the host apparatus;
• a first memory which stores, for each storage area of a predetermined range provided by the plurality of storage devices, counter values indicating the order of the I/Os to and from the storage areas;
• and
• a second memory which stores control information of the I/O requests for each of the I/O requests,
• the data access method comprising steps in which the microprocessors:
• store, if there is one I/O request from the host apparatus, an I/O request range of the one I/O request in an area for storing control information of the one I/O request of the second memory;
• acquire, from the first memory, the counter value of the storage area which is the target of the one I/O request;
• store the counter value in the area for storing control information of the one I/O request of the second memory;
• and
• compare, if the counter value of the one I/O request is greater than the counter value of another I/O request, the I/O request range of the one I/O request stored in the second memory with the I/O request range of the other I/O request;
• and
• if, as a result of comparing the I/O request ranges, there is no overlap between the I/O request ranges, the microprocessors execute the processing of the one I/O request, and if there is an overlap between the I/O request ranges, the microprocessors place the processing of the one I/O request on standby.