On Tue, Oct 09, 2018 at 10:33:48PM +0500, Mikhail Gavrilov wrote: > On Sun, 7 Oct 2018 at 02:20, Eric Sandeen <sandeen@xxxxxxxxxxx> wrote: > > > > On 10/6/18 12:34 PM, Mikhail Gavrilov wrote: > > > Which fragmentation factor is allowable for xfs (not impact on performance)? > > > > > > # xfs_db -c frag -r /dev/sda > > > actual 4908781, ideal 2801391, fragmentation factor 42.93% > > > > Ignore the fragmentation factor, because: > > > > > Note, this number is largely meaningless. > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > http://xfs.org/index.php/XFS_FAQ#Q:_The_xfs_db_.22frag.22_command_says_I.27m_over_50.25._Is_that_bad.3F > > > > > Files on this filesystem average 1.75 extents per file > > The majority of your files have only 1 extent. > > > > > # mount | grep sda > > > /dev/sda on /home type xfs (rw,relatime,seclabel,attr2,inode64,noquota) > > > > > > # df -h | grep sda > > > /dev/sda 11T 5.3T 5.7T 49% /home > > > > > > I think it too much for partition which are half free. > > > > Why do you think that? > > > > > It would also be interesting to see the fragmentation in the context > > > of files, but I have not found anywhere how to look at it. > > > > xfs_bmap will show you extent layout for individual files. > > > > -Eric > > > Thanks I wrote simple bash script for inspect my HDD for top 100 > fragmented files. > Here is my top 100: > > 20511 - /home/mikhail/.local/share/Steam/steamapps/common/Deus Ex > Mankind Divided/share/data/runtime/game.layer.0.all.archive These are almost all steam packages. I'm betting they have a torrent-style download algorithm which effectively makes writing the file random IO. This is why torrent clients tend to use fallocate() these days, so the end result is a contiguous file regardless of the order of file data chunks arriving over the network.... > The biggest concern is the presence file > "/home/mikhail/.cache/tracker/meta.db" in this list. > Because this is a base of indexed files in GNOME. That's not unusual, and given that it's a database that is generally used for random lookups then file fragmentation is mostly irrelevant. > The purpose of my research was to show that despite the fact that with > average 1.75 extents per file, is possible find files on the disk > that, for some unknown reason, are divided on 20K parts. Usually a result of applications doing something unusual and the developers being unaware that they are doing something sub-optimal that can be easily mitigated. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
