| 摘要 |
A copy source device includes bit map acquisition and bit map merge functions. In accordance with bit-map management information in which a bit map indicating the presence of written data is rounded, the bit map acquisition and bit map merger acquires required bit map from a copy destination device, and merges the acquired bit map to a corresponding bit map of the copy source device. The copy destination device includes bit-map management information updater. The bit-map management information updater updates bit-map management information indicating a write operation when the write operation has been performed during a copy suspend mode. During a copy resume mode, the copy source device requests the copy destination device to transfer the bit-map management information, and in response, the copy destination device transfers the bit-map management information.
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