Method and apparatus for reclaiming memory blocks in snapshot storage space

A computer program product for reclaiming one or more chunks in a snapshot storage space, the computer program product comprising:

• a non-transitory computer readable medium encoded with computer-executable code, wherein the code, when executed, causes one or more processors to perform the operations of:
• defining, via a computing device, a predefined trigger event;
• detecting, via the computing device, one or more unused chunks in the snapshot storage space, in response to the predefined trigger event, wherein the one or more unused chunks is an idle chunk, wherein the detecting comprises scanning, via the computing device, a first mapping table that records a storage state of a plurality of chunks in the snapshot storage space to determine the one or more unused chunks in the snapshot storage space, a value in the first mapping table representing whether a corresponding chunk in the snapshot storage space is used;
• de-mapping, via the computing device, the one or more unused chunks from the snapshot storage space;
• reclaiming, via the computing device, the one or more detected unused chunks by providing the one or more detected unused chunks to a storage pool for reuse;
• and
• after providing the one or more detected unused chunks to the storage pool, updating, via the computing device, in a second mapping table that records a reclaiming state of a plurality of chunks in the snapshot storage space, the reclaiming state of the one or more detected unused chunks, each value in the second mapping table representing whether a corresponding chunk in the snapshot storage space has been reclaimed or not reclaimed.