Solid archives

Index

A solid archive is a RAR archive packed by a special compression method, which treats all files, within the archive, as one continuous data stream. Solid archives are supported only by the RAR archiving format, ZIP archives are always non-solid. The archiving method for RAR archives is a user selectable option and may be Solid or non-Solid.

Solid archiving significantly increases compression, especially when adding a large number of small, similar files. But it also has a few important disadvantages:

• slower updating of existing solid archives;
• to extract a single file from a solid archive all preceding files must be analyzed. This makes extraction from the middle of a solid archive slower than extraction from a normal archive, but, if all files are to be extracted from a solid archive, the extraction speed will not be affected.
• if any file in a solid archive is damaged, it will be impossible to extract all files which follow the damaged area. Thus if a solid archive is stored to media such as diskette, it is recommended to make use of the recovery record.

Solid archiving is preferable if:

• the archive is updated rarely;
• it is not necessary to frequently extract a single file or only part of the files from the archive;
• compression ratio is more important than compression speed.

Usually files in a solid archive are sorted by extension. But it is possible to set an alternative file order using a special file, rarfiles.lst.

Volumes and self-extracting archives (SFX) may also be solid.

See also: switch -S, switch -DS, rarfiles.lst