| 摘要 |
This storage device supplies, to a host device, an extension VOL having no correlation (mapping) with a final storage medium, and accepts access to the extension VOL from the host device. The storage device compresses the data written into the extension VOL on-line in a cache memory and correlates the compressed data to a compression VOL which is a volume correlated with the final storage medium. At the same time, the storage device maintains and manages mapping information about an area in the extension VOL into which data is written and a position in the compression VOL to which the compressed data of the written data is correlated, whereby, when a request for read from the extension VOL is received from the host device, the storage device converts information about a position in the extension VOL designated by the read request into information about a position in the final storage medium on the basis of the mapping information, reads out the compressed data from the final storage medium into the cache memory, extends the compressed data in the cache memory, and transfers the extended data to the host device. |
