| 摘要 |
An improved apparatus and method for performing snapshots of a logical volume within a block-level storage devices is disclosed. When a snapshot is created, the logical volume manager determines the blocks in the relevant volume that are not allocated and lists those blocks in an exception table. Upon receiving a write request, the volume manager checks the exception table to determine whether the specific block in question is unallocated. If it is allocated, the volume manager performs a copy-on-write for the block for the snapshot. If it is unallocated, the volume manager does not copy the block. This results in significant efficiency, since copy-on-write operations will not be performed for unallocated blocks within a snapshot volume. |
