Thanks for the insights (also in other responses). On 31.12.19 23:58, Zygo Blaxell wrote: > Two workarounds: > > - use 5.3.18 instead of 5.4.6 > > - use the 'metadata_ratio=1' mount option after balancing a few > data block groups Switched back to 5.3.18. Since the space bug (at least the external/df part) was solved for me before switching, I did not need to do anything further. A full(100%) data balance succeeds successfully now. > In your other mail you indicated you were running a full balance. Full > balances are never useful(*) and will make this specific situation worse. > > A full balance includes a metadata balance. The primary effect > of metadata balance is to temporarily reduce space for metadata. > Reducing metadata space causes an assortment of problems for btrfs, > only one of which is hitting the 5.4 free space bug. For all but a few > contrived test cases, btrfs manages metadata well without interference > from balance. Too much metadata balancing (i.e. any at all) can make > a filesystem truly run out of metadata space on disk--a condition that > is sometimes difficult to reverse. In my situation, my observation was that when I hit the space bug, I had 12GB meta reserved, 10.x used. The first balance lifted reserved space up to 13GB and I have not seen the issue afterwards. So from practice/my observations, it fixed the issue (also see Swamis response). I will take into account your insights in the future, though, and try to not balance metadata. Cheers, Ole
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