On Wednesday 02 December 2015 18:46:30 Tomasz Chmielewski wrote: >What are your disk space savings when using btrfs with compression? > >I have a 200 GB btrfs filesystem which uses compress=zlib, only stores >text files (logs), mostly multi-gigabyte files. > > >It's a "single" filesystem, so "df" output matches "btrfs fi df": > ># df -h >Filesystem Size Used Avail Use% Mounted on >(...) >/dev/xvdb 200G 124G 76G 62% /var/log/remote > > ># du -sh /var/log/remote/ >153G /var/log/remote/ > > > From these numbers (124 GB used where data size is 153 GB), it appears >that we save around 20% with zlib compression enabled. >Is 20% reasonable saving for zlib? Typically text compresses much better >with that algorithm, although I understand that we have several >limitations when applying that on a filesystem level. > > >Tomasz Chmielewski >http://wpkg.org
I have a total of three file systems that use compression, on a desktop and a laptop. / on both uses compress=lzo, and my backup drive uses compress=zlib (my RAID1 FS does not use compression). My desktop looks like this: % df -h Dateisystem Größe Benutzt Verf. Verw% Eingehängt auf /dev/sda1 108G 79G 26G 76% / [...] For / I get a total of about 8G or at least 9% space saving: # du -hsc /mnt/rootfs/* 71G /mnt/rootfs/home 14G /mnt/rootfs/rootfs 2,3G /mnt/rootfs/var 87G insgesamt I write "at least" because this does not include snapshots. On my laptop the difference is merely 1 GB (83 vs. 84 GB), but it was using the autodefrag mount option until yesterday (when I migrated it to an SSD using dd), which probably accounts for a significant amount of wasted space. I'll see how it develops over the next two weeks, but I expect the ratio to become similar to my desktop (probably less, since there is also a lot of music on there). I would love to answer the question for my backup drive, but du took too long (> 1 h) so I stopped it :-( . I might try it again later, but no promises! Greetings -- Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup
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