Am 22.01.2016 um 23:33 schrieb Christian Boltz:
Hello,
I just had an interesting[tm] problem - updating to the latest tumbleweed failed at random places.
It turned out that my btrfs / partition was full. Not with df -h (which reported some GB free), but "btrfs fi show" showed 100% usage. (Sorry for not including the exact output - I didn't save it.)
I faced the problem some weeks ago and reported it here, but did not know the cause. I assumed my 50GB SSD was going bad, because zypper could not unpack the rpms it downloaded anymore. df showed enough free space, and I did not know about "btrfs fi show". I did know how to limit snapshots to a smaller than default number - so I thought that I would already "know" how to use btrfs. I had no idea something could occupy space that df would not show despite maybe bad blocks on the SSD. Nevertheless my gut-feeling told me to delete some stuff, what helped temporarily. But I went back to ext4 at the point I could no longer boot / due to a "half-installed" zypper dup.
I found out [1] that I should run btrfs balance start / -dlimit=3 which freed quite some space. Another run freed even more space, so I decided to run it without the limit: btrfs balance start / After that, I'm down to
# btrfs fi show Label: none uuid: 9f4a918d-fcd4-45d3-a1dc-7b887300eabc Total devices 1 FS bytes used 22.91GiB devid 1 size 50.00GiB used 25.31GiB path /dev/mapper/cboltz-root
snip To understand, I read https://btrfs.wiki.kernel.org/index.php/Balance_Filters and the FAQ. However I do not understand much. What is all those "metadata" and what exactly does balance filter? I do understand what btrfs balance tries to fix (full file system errors), but not how or why the problem exists. Can someone explain in less technical terms?
Should there be a cronjob that does the rebalancing or other btrfs maintenance regularly?
Andrei wrote in a reply to your mail that there is a cron job but disabled by default. Should this be considered a bug? Shouldn´t the default protect the "normal" btrfs user from silently (not shown by df) filling up the filesystem? Or would be a meaningful error message possible? Or a "warning-popup" that says "please consider running btrfs balance to free up btrfs-occupied space"? Thanks Christian and Andrei for the interesting insights so far :) snip
https://btrfs.wiki.kernel.org/index.php/FAQ#Help.21_I_ran_out_of_disk_space....
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