Patent ID: 8108605

Claim:
A data storage system comprising: a first storage device; a second storage device; and a controller configured to gain data access to the first storage device using a first device control module on startup, and to gain data access to the first storage device using a second device control module after the startup, wherein: the first device control module comprises a tracer configured to record, when a write command to write data to the first storage device is received, trace information indicating the write command in the second storage device, and the second device control module comprises a cache-consistency assurance module configured to invalidate, when taking over the write command to write data to the first storage device or a read command to read data therefrom from the first device control module, a data block cached in the second storage device comprising data to be updated as a result of writing of data to the first storage device which is executed by the first device control module before the takeover, the data block comprising read-target data cached in the second storage device based on the trace information when the read-target data is read out of the first storage device upon receipt of the read command to read from the first storage device.