I created a 1TB RAID1. So far it is just for testing, no important data
on there.
After a reboot, I tried to mount it again
# mount /dev/mapper/vg00-btrfsvol0_0 /mnt/btrfs0
mount: wrong fs type, bad option, bad superblock on
/dev/mapper/vg00-btrfsvol0_0,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
I checked dmesg:
[17216.145092] device fsid c959d4a5-0713-4685-b572-8a679ec37e20 devid 1
transid 34 /dev/mapper/vg00-btrfsvol0_0
[17216.145639] btrfs: disk space caching is enabled
[17216.146987] btrfs: failed to read the system array on dm-100
[17216.147556] btrfs: open_ctree failed
Then I did btrfsck - it reported no errors, but mounted OK:
# btrfsck /dev/mapper/vg00-btrfsvol0_0
checking extents
checking fs roots
checking root refs
found 26848493568 bytes used err is 0
total csum bytes: 26170252
total tree bytes: 48517120
total fs tree bytes: 5492736
btree space waste bytes: 14307930
file data blocks allocated: 26799976448
referenced 26799976448
Btrfs Btrfs v0.19
# mount /dev/mapper/vg00-btrfsvol0_0 /mnt/btrfs0
#
I checked dmesg again, these are the messages from the second mount:
[17299.180600] device fsid 928b939f-7f9d-4095-b1ba-e35c5f1277bf devid 1
transid 37928 /dev/dm-96
[17299.204475] device fsid c959d4a5-0713-4685-b572-8a679ec37e20 devid 2
transid 34 /dev/dm-99
[17299.204658] device fsid c959d4a5-0713-4685-b572-8a679ec37e20 devid 1
transid 34 /dev/dm-100
[17299.288317] device fsid 928b939f-7f9d-4095-b1ba-e35c5f1277bf devid 1
transid 37928 /dev/dm-96
[17299.289024] device fsid c959d4a5-0713-4685-b572-8a679ec37e20 devid 2
transid 34 /dev/dm-99
[17299.289150] device fsid c959d4a5-0713-4685-b572-8a679ec37e20 devid 1
transid 34 /dev/dm-100
[17310.978518] device fsid c959d4a5-0713-4685-b572-8a679ec37e20 devid 1
transid 34 /dev/mapper/vg00-btrfsvol0_0
[17310.993882] btrfs: disk space caching is enabled
Can anyone comment on this?
Also, df is reporting double the actual RAID1 volume size, and double
the amount of data stored in this filesystem:
# df -lh .
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg00-btrfsvol0_0 1.9T 51G 1.8T 3% /mnt/btrfs0
I would expect to see Size=1T, Used=25G
# strace -v -e trace=statfs df -lh /mnt/btrfs0
statfs("/mnt/btrfs0", {f_type=0x9123683e, f_bsize=4096,
f_blocks=488374272, f_bfree=475264720, f_bavail=474749786, f_files=0,
f_ffree=0, f_fsid={2083217090, -1714407264}, f_namelen=255,
f_frsize=4096}) = 0
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg00-btrfsvol0_0 1.9T 51G 1.8T 3% /mnt/btrfs0
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