Had to wait for 'btrfs recover' to finish before I proceed farther. Kernel is 4.19.45, tools are 4.19.1
File system is a 3-disk RAID10 with WD3003FZEX (WD Black 3TB) Output from attempting to mount: # mount -o ro,usebackuproot /dev/sdc1 /mnt mount: wrong fs type, bad option, bad superblock on /dev/sdc1, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so. Kernel messages from the mount attempt: [Thu Aug 15 08:47:42 2019] BTRFS info (device sdc1): trying to use backup root at mount time [Thu Aug 15 08:47:42 2019] BTRFS info (device sdc1): disk space caching is enabled [Thu Aug 15 08:47:42 2019] BTRFS info (device sdc1): has skinny extents [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): parent transid verify failed on 229846466560 wanted 49749 found 49750 [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): parent transid verify failed on 229846466560 wanted 49749 found 49750 [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): failed to read block groups: -5 [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): open_ctree failed Output from 'btrfs check -p /dev/sdc1': # btrfs check -p /dev/sdc1 Opening filesystem to check... parent transid verify failed on 229846466560 wanted 49749 found 49750 Ignoring transid failure ERROR: child eb corrupted: parent bytenr=229845336064 item=0 parent level=1 child level=2 ERROR: cannot open file system On 08/15/2019 10:35 +0800, Qu Wenruo wrote: >> >> >> On 2019/8/15 ??????2:32, Tim Walberg wrote: >> > Most of the recommendations I've found online deal with when "wanted" >> is >> > greater than "found", which, if I understand correctly means that one >> or >> > more transactions were interrupted/lost before fully committed. >> >> No matter what the case is, a proper transaction shouldn't have any tree >> block overwritten. >> >> That means, either the FLUSH/FUA of the hardware/lower block layer is >> screwed up, or the COW of tree block is already screwed up. >> >> > >> > Are the recommendations for recovery the same if the system is >> reporting a >> > "wanted" that is less than "found"? >> > >> The salvage is no difference than any transid mismatch, no matter if >> it's larger or smaller. >> >> It depends on the tree block. >> >> Please provide full dmesg output and btrfs check for further advice. >> >> Thanks, >> Qu >> -- +----------------------+ | Tim Walberg | | 830 Carriage Dr. | | Algonquin, IL 60102 | | twalb...@comcast.net | +----------------------+