Compressor::Custom (Extra)

Backup can support any compressor you like. Besides the standard gzip and bzip2 compressors, multi-threaded versions of each are also available, like pigz and pbzip2. There’s also xz, the successor to LZMA, which supports multi-threading as of v5.1.1alpha.

To configure a custom compressor, simply use the following:

Model.new(:my_backup, 'My Backup') do

  # Archives, Databases, etc...

  compress_with Custom do |compression|
    compression.command = 'pbzip2 -p2'
    compression.extension = '.bz2'
  end
end

As long as the compressor accepts input on STDIN and writes to STDOUT, it should work.
i.e. tar -cf - my_files/ | %compression.command% > my_files.tar.%compression.extension%

Also, note that setting defaults for the Custom compressor works the same as with Gzip and Bzip2.

Compressor::Custom.defaults do |compressor|
  compressor.command = 'xz -1'
  compressor.extension = '.xz'
end

Compressor Benchmarks

The following tables provide some benchmarks for gzip, bzip2 and xz using a single CPU core, and using 2 CPU cores. For multi-threaded gzip and bzip2 statistics, pigz and pbzip2 were used. xz supports multi-threaded operation as of v5.1.1alpha.

Keep in mind these are simply provided to give you an idea of the differences between these compressors, and the different levels of compression they support. Compression/Decompression times will vary depending on your system. Memory usage should be the same. If you decide to configure a Custom compressor, you should perform some benchmarks on your own system, and be sure to read the compressor’s documentation.

The source for these tests was a 461 MB tar archive of the Linux Kernel v3.2.12 source distribution.
Entries in bold represent the default settings for the compressor.