BORG-COMPRESSION(1) borg backup tool BORG-COMPRESSION(1)
NAME
borg-compression - Details regarding compression
DESCRIPTION
It is no problem to mix different compression methods in one repo,
deduplication is done on the source data chunks (not on the compressed
or encrypted data).
If some specific chunk was once compressed and stored into the repo,
creating another backup that also uses this chunk will not change the
stored chunk. So if you use different compression specs for the back-
ups, whichever stores a chunk first determines its compression. See
also borg recreate.
Compression is lz4 by default. If you want something else, you have to
specify what you want.
Valid compression specifiers are:
none Do not compress.
lz4 Use lz4 compression. Very high speed, very low compression. (de-
fault)
zstd[,L]
Use zstd ("zstandard") compression, a modern wide-range algo-
rithm. If you do not explicitly give the compression level L
(ranging from 1 to 22), it will use level 3. Archives com-
pressed with zstd are not compatible with borg < 1.1.4.
zlib[,L]
Use zlib ("gz") compression. Medium speed, medium compression.
If you do not explicitly give the compression level L (ranging
from 0 to 9), it will use level 6. Giving level 0 (means "no
compression", but still has zlib protocol overhead) is usually
pointless, you better use "none" compression.
lzma[,L]
Use lzma ("xz") compression. Low speed, high compression. If
you do not explicitly give the compression level L (ranging from
0 to 9), it will use level 6. Giving levels above 6 is point-
less and counterproductive because it does not compress better
due to the buffer size used by borg - but it wastes lots of CPU
cycles and RAM.
auto,C[,L]
Use a built-in heuristic to decide per chunk whether to compress
or not. The heuristic tries with lz4 whether the data is com-
pressible. For incompressible data, it will not use compression
(uses "none"). For compressible data, it uses the given C[,L]
compression - with C[,L] being any valid compression specifier.
obfuscate,SPEC,C[,L]
Use compressed-size obfuscation to make fingerprinting attacks
based on the observable stored chunk size more difficult. Note:
- you must combine this with encryption or it won't make any
sense. - your repo size will be bigger, of course.
The SPEC value will determine how the size obfuscation will
work:
Relative random reciprocal size variation: Size will increase by
a factor, relative to the compressed data size. Smaller factors
are often used, larger factors rarely. 1: factor 0.01 .. 100.0
2: factor 0.1 .. 1000.0 3: factor 1.0 .. 10000.0 4: factor 10.0
.. 100000.0 5: factor 100.0 .. 1000000.0 6: factor 1000.0 ..
10000000.0
Add a randomly sized padding up to the given size: 110: 1kiB ...
120: 1MiB ... 123: 8MiB (max.)
Examples:
borg create --compression lz4 REPO::ARCHIVE data
borg create --compression zstd REPO::ARCHIVE data
borg create --compression zstd,10 REPO::ARCHIVE data
borg create --compression zlib REPO::ARCHIVE data
borg create --compression zlib,1 REPO::ARCHIVE data
borg create --compression auto,lzma,6 REPO::ARCHIVE data
borg create --compression auto,lzma ...
borg create --compression obfuscate,3,none ...
borg create --compression obfuscate,3,auto,zstd,10 ...
borg create --compression obfuscate,2,zstd,6 ...
AUTHOR
The Borg Collective
2023-03-22 BORG-COMPRESSION(1)
Generated by dwww version 1.15 on Sat Jun 29 02:00:58 CEST 2024.