I did have snapshots. Apparently my distro's update utility made these snapshots without clearly telling me... Everything makes sense now. Thanks again for the help.
-- Vasco On Thu, Feb 9, 2017 at 3:53 AM, Qu Wenruo <quwen...@cn.fujitsu.com> wrote: > > > At 02/08/2017 05:55 PM, Vasco Visser wrote: >> >> Thank you for the explanation. What I would still like to know is how >> to relate the chunk level abstraction to the file level abstraction. >> According to the btrfs output there is 2G of data space is available >> and 24G of data space is being used. Does this mean 24G of data used >> in files? > > > Yes, 24G data is used to store data. > (And space cache, while space cache is relatively small, less than 1M for > each chunk) > >> How do I know which files take up most space? du seems >> pretty useless as it reports only 9G of files on the volume. > > > Are you using snapshots? > > If you are only using 1 subvolume(including snapshots), then it seems that > btrfs data CoW waste quite a lot of space. > > In case of btrfs data CoW, for example you have a 128M file(one extent), > then you rewrite 64M of it, your data space usage will be 128M + 64M, as the > first 128M will only be freed after *all* its user get freed. > > For single subvolume and little to none reflink usage case, "btrfs fi > defrag" should help to free some space. > > If you have multiple snapshots or a lot of reflinked files, then I'm afraid > you have to delete some file (including reflink copy or snapshot) to free > some data. > > Thanks, > Qu > > >> >> -- >> Vasco >> >> >> On Wed, Feb 8, 2017 at 4:48 AM, Qu Wenruo <quwen...@cn.fujitsu.com> wrote: >>> >>> >>> >>> At 02/08/2017 12:44 AM, Vasco Visser wrote: >>>> >>>> >>>> Hello, >>>> >>>> My system is or seems to be running out of disk space but I can't find >>>> out how or why. Might be a BTRFS peculiarity, hence posting on this >>>> list. Most indicators seem to suggest I'm filling up, but I can't >>>> trace the disk usage to files on the FS. >>>> >>>> The issue is on my root filesystem on a 28GiB ssd partition (commands >>>> below issued when booted into single user mode): >>>> >>>> >>>> $ df -h >>>> Filesystem Size Used Avail Use% Mounted on >>>> /dev/sda3 28G 26G 2.1G 93% / >>>> >>>> >>>> $ btrfs --version >>>> btrfs-progs v4.4 >>>> >>>> >>>> $ btrfs fi usage / >>>> Overall: >>>> Device size: 27.94GiB >>>> Device allocated: 27.94GiB >>>> Device unallocated: 1.00MiB >>> >>> >>> >>> So from chunk level, your fs is already full. >>> >>> And balance won't success since there is no unallocated space at all. >>> The first 1M of btrfs is always reserved and won't be allocated, and 1M >>> is >>> too small for btrfs to allocate a chunk. >>> >>>> Device missing: 0.00B >>>> Used: 25.03GiB >>>> Free (estimated): 2.37GiB (min: 2.37GiB) >>>> Data ratio: 1.00 >>>> Metadata ratio: 1.00 >>>> Global reserve: 256.00MiB (used: 0.00B) >>>> Data,single: Size:26.69GiB, Used:24.32GiB >>> >>> >>> >>> You still have 2G data space, so you can still write things. >>> >>>> /dev/sda3 26.69GiB >>>> Metadata,single: Size:1.22GiB, Used:731.45MiB >>> >>> >>> >>> Metadata has has less space when considering "Global reserve". >>> In fact the used space would be 987M. >>> >>> But it's still OK for normal write. >>> >>>> /dev/sda3 1.22GiB >>>> System,single: Size:32.00MiB, Used:16.00KiB >>>> /dev/sda3 32.00MiB >>> >>> >>> >>> System chunk can hardly be used up. >>> >>>> Unallocated: >>>> /dev/sda3 1.00MiB >>>> >>>> >>>> $ btrfs fi df / >>>> Data, single: total=26.69GiB, used=24.32GiB >>>> System, single: total=32.00MiB, used=16.00KiB >>>> Metadata, single: total=1.22GiB, used=731.48MiB >>>> GlobalReserve, single: total=256.00MiB, used=0.00B >>>> >>>> >>>> However: >>>> $ mount -o bind / /mnt >>>> $ sudo du -hs /mnt >>>> 9.3G /mnt >>>> >>>> >>>> Try to balance: >>>> $ btrfs balance start / >>>> ERROR: error during balancing '/': No space left on device >>>> >>>> >>>> Am I really filling up? What can explain the huge discrepancy with the >>>> output of du (no open file descriptors on deleted files can explain >>>> this in single user mode) and the FS stats? >>> >>> >>> >>> Just don't believe the vanilla df output for btrfs. >>> >>> For btrfs, unlike other fs like ext4/xfs, which allocates chunk >>> dynamically >>> and has different metadata/data profile, we can only get a clear view of >>> the >>> fs from both chunk level(allocated/unallocated) and extent >>> level(total/used). >>> >>> In your case, your fs doesn't have any unallocated space, this make >>> balance >>> unable to work at all. >>> >>> And your data/metadata usage is quite high, although both has small >>> available space left, the fs should be writable for some time, but not >>> long. >>> >>> To proceed, add a larger device to current fs, and do a balance or just >>> delete the 28G partition then btrfs will handle the rest well. >>> >>> Thanks, >>> Qu >>> >>>> >>>> Any advice on possible causes and how to proceed? >>>> >>>> >>>> -- >>>> Vasco >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" >>>> in >>>> the body of a message to majord...@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>>> >>> >>> >> >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
