On Wed, Dec 2, 2015 at 9:53 PM, Tomasz Chmielewski <t...@virtall.com> wrote: > On 2015-12-02 22:03, Austin S Hemmelgarn wrote: > >>> 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. >> >> >> This is actually an excellent question. A couple of things to note >> before I share what I've seen: >> 1. Text compresses better with any compression algorithm. It is by >> nature highly patterned and moderately redundant data, which is what >> benefits the most from compression. > > > It looks that compress=zlib does not compress very well. Following Duncan's > suggestion, I've changed it to compress-force=zlib, and re-copied the data > to make sure the file are compressed. > > Compression ratio is much much better now (on a slightly changed data set): > > # df -h > /dev/xvdb 200G 24G 176G 12% /var/log/remote > > > # du -sh /var/log/remote/ > 138G /var/log/remote/ > > > So, 138 GB files use just 24 GB on disk - nice! > > However, I would still expect that compress=zlib has almost the same effect > as compress-force=zlib, for 100% text files/logs.
btw, what is your kernel version? there was a bug that detected inode compression ration wrong. http://git.kernel.org/cgit/linux/kernel/git/mason/linux-btrfs.git/commit/?id=68bb462d42a963169bf7acbe106aae08c17129a5 http://git.kernel.org/cgit/linux/kernel/git/mason/linux-btrfs.git/commit/?id=4bcbb33255131adbe481c0467df26d654ce3bc78 Regards, Shilong > > > Tomasz Chmielewski > http://wpkg.org > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
