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Diffstat (limited to 'README')
| -rw-r--r-- | README | 43 |
1 files changed, 22 insertions, 21 deletions
@@ -1,21 +1,21 @@ Description -Tarlz is a combined implementation of the tar archiver and the lzip -compressor. By default tarlz creates, lists and extracts archives in a -simplified posix pax format compressed with lzip on a per file basis. Each -tar member is compressed in its own lzip member, as well as the end-of-file -blocks. This method adds an indexed lzip layer on top of the tar archive, -making it possible to decode the archive safely in parallel. The resulting -multimember tar.lz archive is fully backward compatible with standard tar -tools like GNU tar, which treat it like any other tar.lz archive. Tarlz can -append files to the end of such compressed archives. - -Tarlz can create tar archives with four levels of compression granularity; -per file, per directory, appendable solid, and solid. - -Of course, compressing each file (or each directory) individually is -less efficient than compressing the whole tar archive, but it has the -following advantages: +Tarlz is a massively parallel (multi-threaded) combined implementation of +the tar archiver and the lzip compressor. Tarlz creates, lists and extracts +archives in a simplified posix pax format compressed with lzip, keeping the +alignment between tar members and lzip members. This method adds an indexed +lzip layer on top of the tar archive, making it possible to decode the +archive safely in parallel. The resulting multimember tar.lz archive is +fully backward compatible with standard tar tools like GNU tar, which treat +it like any other tar.lz archive. Tarlz can append files to the end of such +compressed archives. + +Tarlz can create tar archives with five levels of compression granularity; +per file, per block, per directory, appendable solid, and solid. + +Of course, compressing each file (or each directory) individually can't +achieve a compression ratio as high as compressing solidly the whole tar +archive, but it has the following advantages: * The resulting multimember tar.lz archive can be decompressed in parallel, multiplying the decompression speed. @@ -48,14 +48,15 @@ potentially much worse that undetected corruption in the data. Even more so in the case of pax because the amount of metadata it stores is potentially large, making undetected corruption more probable. -Because of the above, tarlz protects the extended records with a CRC in -a way compatible with standard tar tools. +Because of the above, tarlz protects the extended records with a CRC in a +way compatible with standard tar tools. Tarlz does not understand other tar formats like gnu, oldgnu, star or v7. -The diagram below shows the correspondence between each tar member -(formed by one or two headers plus optional data) in the tar archive and -each lzip member in the resulting multimember tar.lz archive: +The diagram below shows the correspondence between each tar member (formed +by one or two headers plus optional data) in the tar archive and each lzip +member in the resulting multimember tar.lz archive, when per file +compression is used: tar +========+======+=================+===============+========+======+========+ |