On Sun, Mar 29, 2020 at 12:42 AM Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx> wrote: > > 90 seconds sounds about right for the block group scan when mounting on > a 10TB filesystem. There's a feature called block group tree in kernel > 5.5 that helps with that: it lays out block group items on disk closer > together so they can be read in milliseconds. This is an on-disk format > change, so once you enable that feature, you wouldn't be able to mount > the filesystem on an older kernel. This can be a problem if your > sound drivers have regressions. You might want to wait a few kernel > releases to be sure you don't need to downgrade. I'm not seeing anything about block group tree in btrfs/super.c. There is block_group_cache_tree but I'm not seeing anything about it in 'man 5 btrfs' using btrfs-progs 5.4, or in the devel branch. So I'm not sure what mount option or btrfstune option this would be, seems to be automatic? https://github.com/kdave/btrfs-progs/commit/2eaf862f46b3ccb6b7248a0417ebf7096bc93b80 -- Chris Murphy
