Basically I'm using btrbk to create snapshots on main disk (MMM) and send them 2 distinct disks (AAA and BBB). I have many nested subvolumes (X, X/foo/Y, etc), so every distinct subvolume is enumerated separately, like X.111, X.112, ..., X/foo/Y.111, X/foo/Y.112, etc. Setup worked well for 100s of snapshots and backups (send/receive) within the last 2 months.
Currently there is one offending subvolume that couldn't be sent to disk AAA (say X.111). I tried to send it a couple of times even though the huge size (230GB, takes 4 hour for every test) but there was no success. Error was like: ERROR: ... sh: btrfs send -p /mnt/MMM-root/snapshots/erik3/rootfs.20210213T0356 -c /mnt/MMM-root/snapshots/erik3/rootfs.20210213T0414 /mnt/MMM-root/snapshots/erik3/home/ceremcem.20210213T0356 | mbuffer -v 1 | btrfs receive /mnt/AAA-root/snapshots/erik3/home/ ERROR: ... cannot open /mnt/AAA-root/snapshots/erik3/home/ceremcem.20210213T0356/o10179316-137012-0: No such file or directory I tried to issue `btrfs send /mnt/MMM-root/snapshots/erik3/home/ceremcem.20210213T0356 | pv > /dev/null` to see if there is anything wrong with the source snapshot, but it succeeded. Skipping the other intermediate attempts, I tried to remove every snapshot in AAA, BBB, reformat AAA and BBB with mkfs.btrfs, deleted all snapshots and created a new set on MMM, tried to send everything from scratch. It failed with nearly the same error (can't remember now) on the same subvolume (/mnt/MMM-root/snapshots/erik3/home/ceremcem.XXX). I ran a btrfs scrub on /mnt/MMM-root and there were no errors. Why do I keep getting this error? uname -a Linux erik3 5.9.0-0.bpo.5-amd64 #1 SMP Debian 5.9.15-1~bpo10+1 (2020-12-31) x86_64 GNU/Linux btrfs-progs v5.10
