16.3. Backup File Compression

The backup file can be compressed with one of the following algorithms: lzo [49], gzip [50] or zstd [51].

Currently, Zstandard (zstd) is the fastest of these three algorithms. Multi-threading is another advantage of zstd over lzo and gzip. Lzo and gzip are more widely used and often installed by default.

You can install pigz [52] as a drop-in replacement for gzip to provide better performance due to multi-threading. For pigz & zstd, the amount of threads/cores can be adjusted. See the configuration options Section 16.7, “Configuration” below.

The extension of the backup file name can usually be used to determine which compression algorithm has been used to create the backup.

.zst

Zstandard (zstd) compression

.gz or .tgz

gzip compression

.lzo

lzo compression

If the backup file name doesn’t end with one of the above file extensions, then it was not compressed by vzdump.



[49] Lempel–Ziv–Oberhumer a lossless data compression algorithm https://en.wikipedia.org/wiki/Lempel-Ziv-Oberhumer

[50] gzip - based on the DEFLATE algorithm https://en.wikipedia.org/wiki/Gzip

[51] Zstandard a lossless data compression algorithm https://en.wikipedia.org/wiki/Zstandard

[52] pigz - parallel implementation of gzip https://zlib.net/pigz/