On Sun, Aug 16, 2015 at 04:33:52PM +0200, Hendrik Friedel wrote: > Hello, > > I am struggling to understand the output of btrfs fi df: > > btrfs fi df /mnt/__Complete_Disk/ > Data, RAID5: total=3.85TiB, used=3.85TiB > System, RAID5: total=32.00MiB, used=576.00KiB > Metadata, RAID5: total=6.46GiB, used=5.14GiB > GlobalReserve, single: total=512.00MiB, used=0.00B > > I have three disks: > > btrfs fi show > Label: none uuid: a8af3832-48c7-4568-861f-e80380dd7e0b > Total devices 3 FS bytes used 3.85TiB > devid 1 size 2.73TiB used 2.73TiB path /dev/sdf > devid 2 size 2.73TiB used 2.24TiB path /dev/sdd > devid 3 size 2.73TiB used 2.73TiB path /dev/sde
Here's your problem -- you've got a RAID 5 filesystem, which has a minimum allocation of 2 devices, but only one device has free space on it for allocation, so no more chunks can be allocated. I'm not sure how it ended up in this situation, but that's what's happened. From btrfs fi df, you've filled up all the existing data allocation, so the usual filtered balance isn't going to help, because there's no space within the existing allocation to compact the storage into. You will need to free up some space on devices 1 and 3, and then run a full balance. There are two ways I can see of doing this: 1) add a small (4-8 GiB, say) block device, do a full balance, and then delete the device again: # btrfs dev add /dev/sdx /mnt/__Complete_Disk # btrfs balance start /mnt/__Complete_Disk # btrfs dev del /dev/sdx /mnt/__Complete_Disk 2) convert a few chunks of the existing FS, on devices 1 and 3, to single, which should free up some space across all the devices, and then run a full balance, and finally convert the single back to RAID 5: # btrfs balance start -dconvert=single,devid=1,limit=4 /mnt/__Complete_Disk # btrfs balance start -dconvert=single,devid=3,limit=4 /mnt/__Complete_Disk # btrfs balance start -dprofiles=raid5 /mnt/__Complete_Disk # btrfs balance start -dconvert=raid5,soft /mnt/__Complete_Disk Hugo. > So I would expect around 5.4TiB to be available. In fact I am > currently using 4.4TiB and the drive seems to be full (I cannot > store more data). > > I went through Marcs Blog post on this, but the hints there did not > help. In particular: > btrfs balance start -dusage=95 /mnt/__Complete_Disk/ (started with 55) > > What's wrong here? > > Regards, > Hendrik > > --- > Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. > https://www.avast.com/antivirus > -- Hugo Mills | ©1973 Unclear Research Ltd hugo@... carfax.org.uk | http://carfax.org.uk/ | PGP: E2AB1DE4 |
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