From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephane Chazelas Subject: Re: wrong values in "df" and "btrfs filesystem df" Date: Mon, 11 Apr 2011 08:29:46 +0100 Message-ID: References: <20110409091141.GE5301@carfax.org.uk> <4DA182DF.6010703@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Hugo Mills , helmut@hullen.de, linux-btrfs@vger.kernel.org To: Miao Xie Return-path: In-Reply-To: <4DA182DF.6010703@cn.fujitsu.com> List-ID: 2011-04-10 18:13:51 +0800, Miao Xie: [...] > >> # 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. > > This value excludes the space that can not be allocated to any block group, > This feature was implemented to fix the bug df command add the disk space, which > can not be allocated to any block group forever, into the "Available" value. > (see the changelog of the commit 6d07bcec969af335d4e35b3921131b7929bd634e) > > This implementation just like fake chunk allocation, but the fake allocation > just allocate the space from two of these three disks, doesn't spread the > stripes over all the disks, which has enough space. [...] Hi Miao, would you care to expand a bit on that. In Helmut's case above where all the drives have at least 1.2TB free, how would there be un-allocatable space? What's the implication of having disks of differing sizes? Does that mean that the extra space on larger disks is lost? Thanks, Stephane