Compression/Encryption service processing

When the Compression/Encryption service runs, it checks each object that’s eligible for compression. If the object isn’t already compressed, it compresses it. If compressing the object doesn’t reduce its size (for example, because it’s already in a compressed format), the Compression/Encryption service marks it as uncompressible and doesn’t try to compress it again in future runs.

You control which objects are eligible for compression by setting criteria in the System Management Console.

In addition to compressing whole objects, the Compression/Encryption service can compress:

  • Parts of multipart objects
  • Chunks for erasure-coded objects
  • Chunks for erasure-coded parts of multipart objects
  • Full copies of the data for objects and parts that are subject to erasure coding before those copies are reduced to chunks

For the purpose of compression:

  • HCP treats parts of multipart objects as individual objects. Eligibility for compression is based on the individual part size, not on the size of the object as a whole.
  • HCP treats chunks for erasure-coded objects and chunks for erasure-coded parts of multipart objects as individual objects. However, eligibility for compression is based on the size of the whole object or part before erasure coding.

By default, the Compression/Encryption service runs only on primary storage. However, you can configure HCP to run the Compression/Encryption service on extended storage as well.

If an object, part, or chunk that was not eligible for compression becomes eligible, the Compression/Encryption service compresses it on its next run. Similarly, if a compressed object, part, or chunk loses its eligibility for compression, the Compression/Encryption service decompresses it on its next run.

NoteMultiple objects, parts, or chunks merged by the Duplicate Elimination service may have differing eligibility for compression. If any one of the objects, parts, or chunks is eligible for compression, the merged object, part, or chunk data is compressed.