On Sat, Apr 09, 2011 at 08:25:00AM +0200, Helmut Hullen wrote: > Hallo, linux-btrfs, > > First I create an array of 2 disks with > > mkfs.btrfs -d raid0 -m raid1 /dev/sdb1 /dev/sdd1 > > and mount it at /srv/MM. > > Then I fill it with about 1,6 TByte. > And then I add /dev/sde1 via > > btrfs device add /dev/sde1 /srv/MM > btrfs filesystem balance /srv/MM > (it run about 20 hours) > > Then I work on it, copy some new files, delete some old files - all > works well. Only > > df /srv/MM > btrfs filesystem df /srv/MM > > show some completely wrong values: > > # df /srv/MM > > Filesystem 1K-blocks Used Available Use% Mounted on > /dev/sdd1 5846053400 1593436456 2898463184 36% /srv/MM > > # btrfs filesystem df /srv/MM > > Data, RAID0: total=1.67TB, used=1.48TB > System, RAID1: total=16.00MB, used=112.00KB > System: total=4.00MB, used=0.00 > Metadata, RAID1: total=3.75GB, used=2.26GB > > # btrfs-show > > Label: MMedia uuid: 120b036a-883f-46aa-bd9a-cb6a1897c8d2 > Total devices 3 FS bytes used 1.48TB > devid 3 size 1.81TB used 573.76GB path /dev/sdb1 > devid 2 size 1.81TB used 573.77GB path /dev/sde1 > devid 1 size 1.82TB used 570.01GB path /dev/sdd1 > > Btrfs Btrfs v0.19 > > ------------------------------------------------ > > "df" shows an "Available" value which isn't related to any real value. I _think_ that value is the amount of space not allocated to any block group. If that's so, then Available (from df) plus the three "total" values (from btrfs fi df) should equal the size value from df. > The sum of "used" and "Available" is far away from the really existent > disk space. When I copy additional files to "/srv/MM" then "used" still > shows the right value, and the sum grows (slowly) to the max. available > space. > > In "btrfs filesystem df /srv/MM" the line > > Data, RAID0: total=1.67TB, used=1.48TB > > shows a "total" value which isn't related to any existent value; maybe > it still shows the used space before adding the third partition. > This (wrong) value seems not to change. It's not wrong -- it simply doesn't mean what you think it does. :) The total value in the output of "btrfs fi df" is the total space allocated to block groups. As the filesystem needs more space, it will allocate more block groups from the available raw storage pool, and the number will go up. This is explained on the wiki at [1]. HTH, Hugo. [1] https://btrfs.wiki.kernel.org/index.php/FAQ#Why_does_df_show_incorrect_free_space_for_my_RAID_volume.3F -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- There are three things you should never see being made: laws, --- standards, and sausages.
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