Adaptive compression using a sampling based heuristic

A non-transitory computer readable storage medium storing program instructions, wherein the program instructions are executable by one or more processors to:

• detect that a unit of storage from a backup client is to be backed up to a storage system;
• in response to the detecting, determining whether to compress the unit of storage,
• wherein the determining comprises
• identifying a location within the unit of storage, wherein
• the identifying comprises
• scanning the unit of storage, wherein
• the scanning comprises comparing density of data stored in
• the unit of storage with a specified data density criterion, and
• the specified data density criterion comprises a ratio of written storage location to unwritten storage locations,
• determining whether the density of the data stored at the location meets the specified data density criterion prior to attempting to compress the data stored at the location, and
• calculating an offset from the beginning of the unit of storage to the location,
• selecting a portion of the unit of storage beginning at the offset, wherein data stored in the portion of the unit of storage comprises the data stored at the location,
• the portion of the unit of storage is smaller than the unit of storage, and
• the portion of the unit of storage begins at the offset from the beginning of the unit of storage and ends before the end of the unit of storage, and
• attempting to compress the data stored in the portion of the unit of storage;
• and
• if the attempting is successful for the portion of the unit of storage, compressing the entirety of the unit of storage.

A system comprising:

• a storage system;
• one or more processing means coupled to the storage system;
• a backup client coupled to the storage system, the backup client comprising
• means for detecting that a unit of storage is to be backed up;
• means for determining whether to compress the unit of storage, wherein the determining is performed in response to the detecting and the determining comprises
• identifying a location within the unit of storage, wherein
• the identifying comprises
• scanning the unit of storage, wherein
• the scanning comprises comparing density of data stored in the unit of storage with a specified data density criterion, and
• the specified data density criterion comprises a ratio of written storage locations to unwritten storage locations,
• determining whether the density of the data stored at the location meets the specified data density criterion prior to attempting to compress the data stored at the location, and
• calculating an offset from the beginning of the unit of storage,
• selecting a portion of the unit of storage beginning at the offset, wherein
• data stored in the portion of the unit of storage comprises the data stored at the location,
• the portion of the unit of storage is smaller than the unit of storage, and
• the portion of the unit of storage begins at the offset from the beginning of the unit of storage and ends before the end of the unit of storage, and
• attempting to compress the data stored in the portion of the unit of storage;
• and
• means for compressing the entirety of the unit of storage if the determining means indicates that the attempting is successful for the portion of the unit of storage.