I have a btrfs raid1 on raspbian (kernel 4.19.75) which overheated. To fix the btrfs filesystem I attached the raid1 to my workstation with Arch Linux (kernel 5.5.1). I run scrub to identify broken files and fixed them. Furthermore I run --full-balance and defrag -r. All fine so far. Now I can't mount the btrfs on raspbian any more (bad superblock). I checked with a blank raspbian and different boards, same result. On my Arch Linux workstation there are no problems. The btrfs changelog [1] only mentions more checksums (xxhash, sha256...) as possible incompatible features between 4.19 and 5.5. However the raid1 is still crc32c (see below). I'm afraid balance/scrub/defrag operations of my Arch Linux made the btrfs raid1 incompatible to older kernels. Is that plausible? How could I convert it back? 4.19.75 dmesg: [ 17.707873] GPT:Primary header thinks Alt. header is not at the end of the di sk. [ 17.707889] GPT:7814037167 != 253879390758629 [ 17.707895] GPT:Alternate GPT header not at the end of the disk. [ 17.707902] GPT:7814037167 != 253879390758629 [ 17.707907] GPT: Use GNU Parted to correct GPT errors. [ 17.707977] sdb: sdb1 [ 17.709682] GPT:Primary header thinks Alt. header is not at the end of the disk. [ 17.709697] GPT:7814037167 != 253879390758629 [ 17.709703] GPT:Alternate GPT header not at the end of the disk. [ 17.709710] GPT:7814037167 != 253879390758629 [ 17.709715] GPT: Use GNU Parted to correct GPT errors. [ 17.709787] sda: sda1 [ 17.710776] sd 0:0:0:1: [sdb] Attached SCSI disk [ 17.721324] sd 0:0:0:0: [sda] Attached SCSI disk [ 18.301910] raid6: int32x1 gen() 203 MB/s [ 18.471765] raid6: int32x1 xor() 178 MB/s [ 18.641705] raid6: int32x2 gen() 278 MB/s [ 18.811703] raid6: int32x2 xor() 207 MB/s [ 18.981816] raid6: int32x4 gen() 307 MB/s [ 19.151686] raid6: int32x4 xor() 228 MB/s [ 19.321816] raid6: int32x8 gen() 315 MB/s [ 19.491762] raid6: int32x8 xor() 219 MB/s [ 19.661699] raid6: neonx1 gen() 711 MB/s [ 19.831664] raid6: neonx1 xor() 811 MB/s [ 20.001711] raid6: neonx2 gen() 1175 MB/s [ 20.171661] raid6: neonx2 xor() 1187 MB/s [ 20.341685] raid6: neonx4 gen() 1550 MB/s [ 20.511663] raid6: neonx4 xor() 1344 MB/s [ 20.681678] raid6: neonx8 gen() 1371 MB/s [ 20.851667] raid6: neonx8 xor() 1125 MB/s [ 20.851673] raid6: using algorithm neonx4 gen() 1550 MB/s [ 20.851676] raid6: .... xor() 1344 MB/s, rmw enabled [ 20.851680] raid6: using neon recovery algorithm [ 20.881255] xor: measuring software checksum speed [ 20.971664] arm4regs : 2020.800 MB/sec [ 21.071659] 8regs : 1357.600 MB/sec [ 21.171657] 32regs : 1262.800 MB/sec [ 21.271658] neon : 2156.800 MB/sec [ 21.271664] xor: using function: neon (2156.800 MB/sec) [ 21.417002] Btrfs loaded, crc32c=crc32c-generic [ 21.418650] BTRFS: device label URAID devid 8 transid 1254272 /dev/sdb1 [ 21.423593] BTRFS: device label URAID devid 7 transid 1254272 /dev/sda1 [ 313.823521] BTRFS info (device sda1): disk space caching is enabled [ 313.823537] BTRFS info (device sda1): has skinny extents [ 313.826597] BTRFS critical (device sda1): unable to find logical 3746684731392 length 4096 [ 313.839009] BTRFS critical (device sda1): unable to find logical 3746684731392 length 4096 [ 313.851766] BTRFS critical (device sda1): unable to find logical 3746684731392 length 4096 [ 313.864676] BTRFS critical (device sda1): unable to find logical 3746684731392 length 4096 [ 313.878039] BTRFS critical (device sda1): unable to find logical 3746684731392 length 4096 [ 313.891649] BTRFS critical (device sda1): unable to find logical 3746684731392 length 4096 [ 313.905782] BTRFS error (device sda1): failed to read chunk root [ 313.942529] BTRFS error (device sda1): open_ctree failed btrfs inspect-internal dump-super /dev/disk/by-label/URAID superblock: bytenr=65536, device=/dev/disk/by-label/URAID --------------------------------------------------------- csum_type 0 (crc32c) csum_size 4 csum 0x33567328 [match] bytenr 65536 flags 0x1 ( WRITTEN ) magic _BHRfS_M [match] fsid da28e00e-6ae7-4a28-9bf4-6826157c7e43 metadata_uuid da28e00e-6ae7-4a28-9bf4-6826157c7e43 label URAID generation 1254278 root 14868497367040 sys_array_size 129 chunk_root_generation 1254275 root_level 1 chunk_root 21338870824960 chunk_root_level 1 log_root 0 log_root_transid 0 log_root_level 0 total_bytes 8001571065856 bytes_used 2903387471872 sectorsize 4096 nodesize 16384 leafsize (deprecated) 16384 stripesize 4096 root_dir 6 num_devices 2 compat_flags 0x0 compat_ro_flags 0x0 incompat_flags 0x161 ( MIXED_BACKREF | BIG_METADATA | EXTENDED_IREF | SKINNY_METADATA ) cache_generation 1254278 uuid_tree_generation 1254278 dev_item.uuid fd1a07a5-4cdc-41eb-9776-d4519f2d086b dev_item.fsid da28e00e-6ae7-4a28-9bf4-6826157c7e43 [match] dev_item.type 0 dev_item.total_bytes 4000785104896 dev_item.bytes_used 2931348733952 dev_item.io_align 4096 dev_item.io_width 4096 dev_item.sector_size 4096 dev_item.devid 8 dev_item.dev_group 0 dev_item.seek_speed 0 dev_item.bandwidth 0 dev_item.generation 0 [1] https://btrfs.wiki.kernel.org/index.php/Changelog#By_feature