A method of operating a storage system includes moving a block of data
stored in the storage system to a new location in the storage system,
such as for purposes of defragmentation. After the block has been moved
to the new location, the storage system receives a request requiring
access to the block. The storage system uses metadata appended to an
identified block to detect that the block may have been relocated. The
metadata can further be used to distinguish a block that has been
relocated from a lost write.