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borg help compression, fixes #1582
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Thomas Waldmann
parent
d3e79c4e49
commit
d6bfdafdef
1 changed files with 96 additions and 21 deletions
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@ -1258,6 +1258,92 @@ def do_break_lock(self, args, repository):
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borg create /path/to/repo::{hostname}-{user}-{utcnow} ...
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borg create /path/to/repo::{hostname}-{now:%Y-%m-%d_%H:%M:%S} ...
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borg prune --prefix '{hostname}-' ...\n\n''')
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helptext['compression'] = textwrap.dedent('''
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Compression is off by default, if you want some, you have to specify what you want.
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Valid compression specifiers are:
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none
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Do not compress. (default)
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lz4
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Use lz4 compression. High speed, low compression.
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zlib[,L]
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Use zlib ("gz") compression. Medium speed, medium compression.
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If you do not explicitely give the compression level L (ranging from 0
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to 9), it will use level 6.
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Giving level 0 (means "no compression", but still has zlib protocol
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overhead) is usually pointless, you better use "none" compression.
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lzma[,L]
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Use lzma ("xz") compression. Low speed, high compression.
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If you do not explicitely give the compression level L (ranging from 0
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to 9), it will use level 6.
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Giving levels above 6 is pointless and counterproductive because it does
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not compress better due to the buffer size used by borg - but it wastes
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lots of CPU cycles and RAM.
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auto,C[,L]
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Use a built-in heuristic to decide per chunk whether to compress or not.
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The heuristic tries with lz4 whether the data is compressible.
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For incompressible data, it will not use compression (uses "none").
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For compressible data, it uses the given C[,L] compression - with C[,L]
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being any valid compression specifier.
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The decision about which compression to use is done by borg like this:
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1. find a compression specifier (per file):
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match the path/filename against all patterns in all --compression-from
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files (if any). If a pattern matches, use the compression spec given for
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that pattern. If no pattern matches (and also if you do not give any
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--compression-from option), default to the compression spec given by
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--compression. See docs/misc/compression.conf for an example config.
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2. if the found compression spec is not "auto", the decision is taken:
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use the found compression spec.
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3. if the found compression spec is "auto", test compressibility of each
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chunk using lz4.
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If it is compressible, use the C,[L] compression spec given within the
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"auto" specifier. If it is not compressible, use no compression.
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Examples::
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borg create --compression lz4 REPO::ARCHIVE data
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borg create --compression zlib REPO::ARCHIVE data
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borg create --compression zlib,1 REPO::ARCHIVE data
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borg create --compression auto,lzma,6 REPO::ARCHIVE data
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borg create --compression-from compression.conf --compression auto,lzma ...
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compression.conf has entries like:
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# example config file for --compression-from option
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#
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# Format of non-comment / non-empty lines:
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# <compression-spec>:<path/filename pattern>
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# compression-spec is same format as for --compression option
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# path/filename pattern is same format as for --exclude option
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none:*.gz
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none:*.zip
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none:*.mp3
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none:*.ogg
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General remarks:
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It is no problem to mix different compression methods in one repo,
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deduplication is done on the source data chunks (not on the compressed
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or encrypted data).
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If some specific chunk was once compressed and stored into the repo, creating
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another backup that also uses this chunk will not change the stored chunk.
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So if you use different compression specs for the backups, whichever stores a
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chunk first determines its compression. See also borg recreate.\n\n''')
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def do_help(self, parser, commands, args):
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if not args.topic:
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@ -1624,19 +1710,13 @@ def build_parser(self, prog=None):
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help='specify the chunker parameters. default: %d,%d,%d,%d' % CHUNKER_PARAMS)
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archive_group.add_argument('-C', '--compression', dest='compression',
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type=CompressionSpec, default=dict(name='none'), metavar='COMPRESSION',
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help='select compression algorithm (and level):\n'
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'none == no compression (default),\n'
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'auto,C[,L] == built-in heuristic (try with lz4 whether the data is\n'
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' compressible) decides between none or C[,L] - with C[,L]\n'
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' being any valid compression algorithm (and optional level),\n'
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'lz4 == lz4,\n'
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'zlib == zlib (default level 6),\n'
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'zlib,0 .. zlib,9 == zlib (with level 0..9),\n'
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'lzma == lzma (default level 6),\n'
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'lzma,0 .. lzma,9 == lzma (with level 0..9).')
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help='select compression algorithm, see the output of the '
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'"borg help compression" command for details.')
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archive_group.add_argument('--compression-from', dest='compression_files',
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type=argparse.FileType('r'), action='append',
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metavar='COMPRESSIONCONFIG', help='read compression patterns from COMPRESSIONCONFIG, one per line')
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metavar='COMPRESSIONCONFIG',
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help='read compression patterns from COMPRESSIONCONFIG, see the output of the '
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'"borg help compression" command for details.')
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subparser.add_argument('location', metavar='ARCHIVE',
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type=location_validator(archive=True),
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@ -2146,21 +2226,16 @@ def build_parser(self, prog=None):
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'alternatively, give a reference file/directory.')
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archive_group.add_argument('-C', '--compression', dest='compression',
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type=CompressionSpec, default=None, metavar='COMPRESSION',
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help='select compression algorithm (and level):\n'
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'none == no compression (default),\n'
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'auto,C[,L] == built-in heuristic decides between none or C[,L] - with C[,L]\n'
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' being any valid compression algorithm (and optional level),\n'
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'lz4 == lz4,\n'
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'zlib == zlib (default level 6),\n'
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'zlib,0 .. zlib,9 == zlib (with level 0..9),\n'
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'lzma == lzma (default level 6),\n'
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'lzma,0 .. lzma,9 == lzma (with level 0..9).')
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help='select compression algorithm, see the output of the '
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'"borg help compression" command for details.')
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archive_group.add_argument('--always-recompress', dest='always_recompress', action='store_true',
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help='always recompress chunks, don\'t skip chunks already compressed with the same'
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'algorithm.')
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archive_group.add_argument('--compression-from', dest='compression_files',
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type=argparse.FileType('r'), action='append',
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metavar='COMPRESSIONCONFIG', help='read compression patterns from COMPRESSIONCONFIG, one per line')
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metavar='COMPRESSIONCONFIG',
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help='read compression patterns from COMPRESSIONCONFIG, see the output of the '
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'"borg help compression" command for details.')
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archive_group.add_argument('--chunker-params', dest='chunker_params',
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type=ChunkerParams, default=None,
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metavar='CHUNK_MIN_EXP,CHUNK_MAX_EXP,HASH_MASK_BITS,HASH_WINDOW_SIZE',
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