I was in the middle of replacing the drives of my NAS one-by-one (I
wished to move to bigger and faster storage at the end), so I used one
more SATA drive + SATA cable than usual. Unfortunately, the extra
cable turned out to be faulty and it looks like it caused some heavy
damage to the file system.
There was no "devive replace" running at the moment or the disaster.
The first round already got finished hours ago and I planned to start
the next one before going to sleep. So, it was a full RAID-5 setup in
normal state. But one of the active, mounted devices was the first
replacment HDD and it was hanging on the spare SATA cable.
I tried to save some file to my mounted samba share and I realized the
file system because read-only. I rebooted the machine and saw that my
/data can't be mounted.
According to SmartmonTools, one of the drives was suffering from SATA
communication errors.
I tried some tirivial recovery methods and I tried to search the
mailing list archives but I didn't really find a solution. I wonder if
somebody can help with this.
Should I run "btrfs rescue chunk-recover /dev/sda"?
Here are some raw details:
# uname -a
Linux F17a_NAS 4.2.3-gentoo #2 SMP Sun Oct 18 17:56:45 CEST 2015
x86_64 AMD E-350 Processor AuthenticAMD GNU/Linux
# btrfs --version
btrfs-progs v4.2.2
# btrfs check /dev/sda
checksum verify failed on 21102592 found 295F0086 wanted 00000000
checksum verify failed on 21102592 found 295F0086 wanted 00000000
checksum verify failed on 21102592 found 99D0FC26 wanted B08FFCA0
checksum verify failed on 21102592 found 99D0FC26 wanted B08FFCA0
bytenr mismatch, want=21102592, have=65536
Couldn't read chunk root
Couldn't open file system
# mount /dev/sda /data -o ro,recovery
mount: wrong fs type, bad option, bad superblock on /dev/sda, ...
# cat /proc/kmsg
<6>[ 1902.033164] BTRFS info (device sdb): enabling auto recovery
<6>[ 1902.033184] BTRFS info (device sdb): disk space caching is enabled
<6>[ 1902.033191] BTRFS: has skinny extents
<3>[ 1902.034931] BTRFS (device sdb): bad tree block start 0 21102592
<3>[ 1902.051259] BTRFS (device sdb): parent transid verify failed on
21147648 wanted 101748 found 101124
<3>[ 1902.111807] BTRFS (device sdb): parent transid verify failed on
44613632 wanted 101770 found 101233
<3>[ 1902.126529] BTRFS (device sdb): parent transid verify failed on
40595456 wanted 101767 found 101232
<6>[ 1902.164667] BTRFS: bdev /dev/sda errs: wr 858, rd 8057, flush
280, corrupt 0, gen 0
<3>[ 1902.165929] BTRFS (device sdb): parent transid verify failed on
44617728 wanted 101770 found 101233
<3>[ 1902.166975] BTRFS (device sdb): parent transid verify failed on
44621824 wanted 101770 found 101233
<3>[ 1902.271296] BTRFS (device sdb): parent transid verify failed on
38621184 wanted 101765 found 101223
<3>[ 1902.380526] BTRFS (device sdb): parent transid verify failed on
38719488 wanted 101765 found 101223
<3>[ 1902.381510] BTRFS (device sdb): parent transid verify failed on
38719488 wanted 101765 found 101223
<3>[ 1902.381549] BTRFS: Failed to read block groups: -5
<3>[ 1902.394835] BTRFS: open_ctree failed
<6>[ 1911.202254] BTRFS info (device sdb): enabling auto recovery
<6>[ 1911.202270] BTRFS info (device sdb): disk space caching is enabled
<6>[ 1911.202275] BTRFS: has skinny extents
<3>[ 1911.203611] BTRFS (device sdb): bad tree block start 0 21102592
<3>[ 1911.204803] BTRFS (device sdb): parent transid verify failed on
21147648 wanted 101748 found 101124
<3>[ 1911.246384] BTRFS (device sdb): parent transid verify failed on
44613632 wanted 101770 found 101233
<3>[ 1911.248729] BTRFS (device sdb): parent transid verify failed on
40595456 wanted 101767 found 101232
<6>[ 1911.251658] BTRFS: bdev /dev/sda errs: wr 858, rd 8057, flush
280, corrupt 0, gen 0
<3>[ 1911.252485] BTRFS (device sdb): parent transid verify failed on
44617728 wanted 101770 found 101233
<3>[ 1911.253542] BTRFS (device sdb): parent transid verify failed on
44621824 wanted 101770 found 101233
<3>[ 1911.278414] BTRFS (device sdb): parent transid verify failed on
38621184 wanted 101765 found 101223
<3>[ 1911.283950] BTRFS (device sdb): parent transid verify failed on
38719488 wanted 101765 found 101223
<3>[ 1911.284835] BTRFS (device sdb): parent transid verify failed on
38719488 wanted 101765 found 101223
<3>[ 1911.284873] BTRFS: Failed to read block groups: -5
<3>[ 1911.298783] BTRFS: open_ctree failed
# btrfs-show-super /dev/sda
superblock: bytenr=65536, device=/dev/sda
---------------------------------------------------------
csum 0xe8789014 [match]
bytenr 65536
flags 0x1
( WRITTEN )
magic _BHRfS_M [match]
fsid 2bba7cff-b4bf-4554-bee4-66f69c761ec4
label
generation 101480
root 37892096
sys_array_size 258
chunk_root_generation 101124
root_level 2
chunk_root 21147648
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 6001196802048
bytes_used 3593129504768
sectorsize 4096
nodesize 4096
leafsize 4096
stripesize 4096
root_dir 6
num_devices 3
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0x381
( MIXED_BACKREF |
RAID56 |
SKINNY_METADATA |
NO_HOLES )
csum_type 0
csum_size 4
cache_generation 101480
uuid_tree_generation 101480
dev_item.uuid 330c9c98-4140-497a-814f-ac76a5b07172
dev_item.fsid 2bba7cff-b4bf-4554-bee4-66f69c761ec4 [match]
dev_item.type 0
dev_item.total_bytes 2000398934016
dev_item.bytes_used 1809263362048
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 2
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0
# btrfs-show-super /dev/sdb
superblock: bytenr=65536, device=/dev/sdb
---------------------------------------------------------
csum 0x177aae67 [match]
bytenr 65536
flags 0x1
( WRITTEN )
magic _BHRfS_M [match]
fsid 2bba7cff-b4bf-4554-bee4-66f69c761ec4
label
generation 101770
root 44650496
sys_array_size 258
chunk_root_generation 101748
root_level 2
chunk_root 21102592
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 6001196802048
bytes_used 3533993762816
sectorsize 4096
nodesize 4096
leafsize 4096
stripesize 4096
root_dir 6
num_devices 3
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0x381
( MIXED_BACKREF |
RAID56 |
SKINNY_METADATA |
NO_HOLES )
csum_type 0
csum_size 4
cache_generation 101770
uuid_tree_generation 101770
dev_item.uuid f14b343e-b701-47f2-a652-e52a47be42b2
dev_item.fsid 2bba7cff-b4bf-4554-bee4-66f69c761ec4 [match]
dev_item.type 0
dev_item.total_bytes 2000398934016
dev_item.bytes_used 1815705812992
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 3
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0
# btrfs-show-super /dev/sdc
superblock: bytenr=65536, device=/dev/sdc
---------------------------------------------------------
csum 0xa06026f3 [match]
bytenr 65536
flags 0x1
( WRITTEN )
magic _BHRfS_M [match]
fsid 2bba7cff-b4bf-4554-bee4-66f69c761ec4
label
generation 101770
root 44650496
sys_array_size 258
chunk_root_generation 101748
root_level 2
chunk_root 21102592
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 6001196802048
bytes_used 3533993762816
sectorsize 4096
nodesize 4096
leafsize 4096
stripesize 4096
root_dir 6
num_devices 3
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0x381
( MIXED_BACKREF |
RAID56 |
SKINNY_METADATA |
NO_HOLES )
csum_type 0
csum_size 4
cache_generation 101770
uuid_tree_generation 101770
dev_item.uuid 4dadced6-392f-4d57-920c-ee8fbebbd608
dev_item.fsid 2bba7cff-b4bf-4554-bee4-66f69c761ec4 [match]
dev_item.type 0
dev_item.total_bytes 2000398934016
dev_item.bytes_used 1815726784512
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 1
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0
# smartctl -a /dev/sda
smartctl 6.4 2015-06-04 r4109 [x86_64-linux-4.2.3-gentoo] (local build)
...
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE
UPDATED WHEN_FAILED RAW_VALUE
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age
Always - 16
This was a new drive and this counter didn't move before I thouched
the cables again in order to prepare for the next "device replace"
round.
I checked the SMART data several times before, during and after the
first round of "device replace" to make sure the new drive didn't came
as faulty from the factory/reseller... I sure these two (unmountable
filesystem and this SATA cable error counter) are directly related.
I threw away these SATA cables because another one of this "batch" (a
four-pack I picked up somewhere, sometime...) proved to be faulty as
well (although that one didn't cause any practical harm, other than
making a Windows PC hanging and the CRC error counter of the SSD
rising).
I am not really happy that Btrfs in RAID5 mode wasn't a little more
fault tolerant towards "disk" faults. Although it might still be
saved, right? Right? :)
Thank you for your answers in advance!
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