From: Calvin Walton <calvin.walton@kepstin.ca>
To: Hugo Mills <hugo-lkml@carfax.org.uk>
Cc: helmut@hullen.de, linux-btrfs@vger.kernel.org
Subject: Re: wrong values in "df" and "btrfs filesystem df"
Date: Sat, 09 Apr 2011 12:36:34 -0400 [thread overview]
Message-ID: <1302366997.19697.3.camel@nayuki> (raw)
In-Reply-To: <20110409091141.GE5301@carfax.org.uk>
On Sat, 2011-04-09 at 10:11 +0100, Hugo Mills wrote:
> 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:
> 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].
And I just drew up a picture which I think should help explain it a bit,
too: http://www.kepstin.ca/dump/btrfs-alloc.png
If I can figure out how to add images to the btrfs wiki, and find a good
place to put it, do you think this would be a helpful addition?
> [1] https://btrfs.wiki.kernel.org/index.php/FAQ#Why_does_df_show_incorrect_free_space_for_my_RAID_volume.3F
--
Calvin Walton <calvin.walton@kepstin.ca>
next prev parent reply other threads:[~2011-04-09 16:36 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-09 6:25 wrong values in "df" and "btrfs filesystem df" Helmut Hullen
2011-04-09 9:11 ` Hugo Mills
2011-04-09 9:46 ` Stephane Chazelas
2011-04-09 12:28 ` Helmut Hullen
2011-04-09 16:36 ` Calvin Walton [this message]
2011-04-09 17:05 ` Helmut Hullen
2011-04-09 17:26 ` Calvin Walton
2011-04-09 18:15 ` Helmut Hullen
2011-04-09 19:35 ` Peter Stuge
2011-04-09 20:38 ` Hugo Mills
2011-04-10 10:13 ` Miao Xie
2011-04-11 7:29 ` Stephane Chazelas
2011-04-11 7:56 ` Arne Jansen
2011-04-11 9:06 ` Helmut Hullen
2011-04-12 7:22 ` Miao Xie
2011-04-12 8:17 ` Stephane Chazelas
2011-04-13 5:35 ` Miao Xie
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1302366997.19697.3.camel@nayuki \
--to=calvin.walton@kepstin.ca \
--cc=helmut@hullen.de \
--cc=hugo-lkml@carfax.org.uk \
--cc=linux-btrfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).