Solid compression

In computing, solid compression is a method for data compression of multiple files, wherein all the uncompressed files are concatenated and treated as a single data block.

One can combine these in two natural ways: The order matters (these operations do not commute), and the latter is solid compression.

In Unix, compression and archiving are traditionally separate operations, which allows one to understand this distinction: A rough graphical representation: In this example, three files each have a common part with the same information, a unique part with information not in the other files, and an "air" part with low-entropy and accordingly well-compressible information.

It can also be efficient when archiving a large number of small files.

[5] Additionally, if the archive becomes even slightly damaged, some of the data (sometimes even all data) after the damaged part in the block can be unusable (depending on the compression and archiving format), whereas in a non-solid archive format, usually only one file is unusable and the subsequent files can usually still be extracted.