| 摘要 |
<p>A method for providing a static snapshot, or image, of data stored on a mass storage system (104). At the start of the method, a preservation memory (106) is cleared and a virtual device is created. Whenever a write is to be performed on the mass storage system (104), a check is made of the preservation memory (106) to determine if it contains a block associated with the mass storage write address. If there is not, a copy of the block in the mass storage system (104) at the block write address is placed in the preservation memory (106). Whenever a read is to be performed on the virtual device, a check is made of the preservation memory (106) to determine if it contains a block associated with the virtual device read address. If there is such a block, that block is returned as the result of the virtual device read. Otherwise, the block at the virtual device block read address is returned as the result.</p> |
