node9:~ # btrfs fi show /dev/sdj
warning, device 1 is missing
warning, device 1 is missing
bytenr mismatch, want=3325407805440, have=0
Couldn't read chunk root
Label: 'local00'  uuid: df5169b9-d0ee-4359-8f57-3ede4e84dcec
        Total devices 2 FS bytes used 2.60TiB
        devid    2 size 2.73TiB used 2.59TiB path /dev/sdj
        *** Some devices missing

btrfs-progs v4.2+20150903
node9:~ # mount -o degraded,ro /dev/sdj
mount: wrong fs type, bad option, bad superblock on /dev/sdj,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
node9:~ # dmesg|tail
[ 4835.930721] BTRFS info (device sdj): enabling auto defrag
[ 4835.930730] BTRFS info (device sdj): allowing degraded mounts
[ 4835.930733] BTRFS info (device sdj): disk space caching is enabled
[ 4835.933132] BTRFS: failed to read chunk root on sdj
[ 4835.952098] BTRFS: open_ctree failed
[ 5065.138499] BTRFS info (device sdj): enabling auto defrag
[ 5065.138505] BTRFS info (device sdj): allowing degraded mounts
[ 5065.138507] BTRFS info (device sdj): disk space caching is enabled
[ 5065.140058] BTRFS: failed to read chunk root on sdj
[ 5065.160210] BTRFS: open_ctree failed