I’ve recently come across a hard file-system error:
BTRFS critical (device sda2): corrupt leaf, slot offset bad: block=43231330304,root=1, slot=47It was on my BTRFS file system on top of an SSD (Solid-state drive).
Despite the error message, it turned out that the problem was not at the file-system level but more at the hard-drive level. I had 100+ sectors that were not readable anymore (according to badblocks)
The solution was to reset the SSD with an ATA instruction “Secure Erase”, and to reinstall a brand new file-system.
# see https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase
hdparm --user-master u --security-erase Eins /dev/Troubleshooting
How to identify the corrupted files?
$ btrfs scrub status /mount-pointthen check the path in dmesg:
BTRFS: i/o error at logical 167135232000 on dev /dev/sda2, sector 213189792, root 5,
inode 2963892, offset 7700480, length 4096, links 1 (path: /home/foo...)Solution by Duncan [3], thanks
How to identify bad sectors?
run badblocks
$ badblocks -b 512 -n /dev/sda(with “-b 512”, the number you obtain corresponds to the sector id to be given to hdparm, see below)
How to know whether there are reallocated sectors?
smartctl -A /dev/sdaRow “Reallocated_Sector_Ct” (ID #5).
Note that this row contains several values and Each Attribute also has a Threshold value (whose range is 0 to 255) which is printed under the heading “THRESH”. If the Normalized value (column Value) is less than or equal to the Threshold value, then the Attribute is said to have failed. If the Attribute is a pre-failure Attribute, then disk failure is imminent. (see man page [4])
smartctl -x /dev/sda gives a wealth of additional information.
How to test a low-level read error?
Once you’ve identified a bad sector, you can test it with hdparm:
hdparm --read-sector 213189792 /dev/sdaIf there is an error, you’ll get something like reading sector 213189792: FAILED: Input/output error
How to force re-allocation?
For a specific sector, use hdparm, see [5], [6]
For the whole drive, use badblocks [7]
badblocks -w /dev/sdaThe EXT4 file system has an option to check for bad blocks at creation time (mkfs.ext4 -cc). It may be a good idea, this forces sector reallocation before putting any important data on the disk [8].
How to run the drive firmware self-tests?
smartct -t long /dev/sdaTo get the results: smartctl -x /dev/sda
Open questions
How to identify the corrupted files from a block identifier (block=43231330304)?
What’s the difference between ATA Security Erase and ATA Enhanced Security Erase?
What does smartctl’s “Runtime_Bad_Block” field mean?
Does a bad sector indicate a failing SSD? Not clear, see [9] and [10]
What is indeed the root cause of the problem? Is it in BTRFS? in the SSD firmware? Because of my use of ecryptfs on top of btrfs on top of a SSD?
References
[1] https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase
[2] http://unix.stackexchange.com/questions/196824/how-to-list-files-part-of-a-btrfs-block
[3] https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg43280.html
[4] http://manpages.ubuntu.com/manpages/hardy/man8/smartctl.8.html
[5] http://serverfault.com/questions/461203/how-to-use-hdparm-to-fix-a-pending-sector
[6] http://www.sj-vs.net/forcing-a-hard-disk-to-reallocate-bad-sectors/
[7] https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg43312.html
[8] http://www.spinics.net/lists/linux-btrfs/msg40909.html
[9] http://unix.stackexchange.com/questions/99553/does-a-bad-sector-indicate-a-failing-disk
[10] https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg43317.html
Errors
[ 7695.806090] BTRFS: i/o error at logical 167135232000 on dev /dev/sda2, sector 213189792, root 5,
inode 2963892, offset 7700480, length 4096, links 1 (path: home/martin/foo)
[ 7695.806097] BTRFS: bdev /dev/sda2 errs: wr 0, rd 401, flush 0, corrupt 0, gen 0
[ 7695.812770] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
[ 7695.812774] ata1.00: irq_stat 0x40000001
[ 7695.812778] ata1.00: failed command: READ DMA
[ 7695.812783] ata1.00: cmd c8/00:08:a0:dc:91/00:00:00:00:00/ee tag 23 dma 4096 in
res 51/40:00:00:00:00/00:00:00:00:00/ee Emask 0x9 (media error)
[ 7695.812785] ata1.00: status: { DRDY ERR }
[ 7695.812786] ata1.00: error: { UNC }
[ 7695.813013] ata1.00: supports DRM functions and may not be fully accessible
[ 7695.813210] ata1.00: failed to get NCQ Send/Recv Log Emask 0x1
[ 7695.813770] ata1.00: supports DRM functions and may not be fully accessible
[ 7695.813859] ata1.00: failed to get NCQ Send/Recv Log Emask 0x1
[ 7695.814164] ata1.00: configured for UDMA/133
[ 7695.814179] sd 0:0:0:0: [sda] Unhandled sense code
[ 7695.814181] sd 0:0:0:0: [sda]
[ 7695.814182] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 7695.814183] sd 0:0:0:0: [sda]
[ 7695.814185] Sense Key : Medium Error [current] [descriptor]
[ 7695.814187] Descriptor sense data with sense descriptors (in hex):
[ 7695.814188] 72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
[ 7695.814195] 0e 00 00 00
[ 7695.814198] sd 0:0:0:0: [sda]
[ 7695.814199] Add. Sense: Unrecovered read error - auto reallocate failed
[ 7695.814201] sd 0:0:0:0: [sda] CDB:
[ 7695.814202] Read(10): 28 00 0e 91 dc a0 00 00 08 00
[ 7695.814208] end_request: I/O error, dev sda, sector 244440224
[ 7695.814222] ata1: EH complete
[ 7695.814227] BTRFS: unable to fixup (regular) error at logical 167135232000 on dev /dev/sda2$ smartctl -x /dev/sda
smartctl -x /dev/sda
smartctl 6.4 2014-10-07 r4002 [x86_64-linux-3.16.0-4-amd64] (local build)
Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org
=== START OF INFORMATION SECTION ===
Device Model: SAMSUNG MZ7PD256HCGM-000H7
Serial Number: S1N8NSAGC23049
LU WWN Device Id: 5 012548 500000000
Firmware Version: DXM06H6Q
User Capacity: 256,060,514,304 bytes [256 GB]
Sector Size: 512 bytes logical/physical
Rotation Rate: Solid State Device
Device is: Not in smartctl database [for details use: -P showall]
ATA Version is: ACS-2, ATA8-ACS T13/1699-D revision 4c
SATA Version is: SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is: Sat Apr 25 19:45:38 2015 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
AAM feature is: Unavailable
APM feature is: Unavailable
Rd look-ahead is: Enabled
Write cache is: Enabled
ATA Security is: Disabled, NOT FROZEN [SEC1]
Wt Cache Reorder: Enabled
=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
General SMART Values:
Offline data collection status: (0x02) Offline data collection activity
was completed without error.
Auto Offline Data Collection: Disabled.
Self-test execution status: ( 0) The previous self-test routine completed
without error or no self-test has ever
been run.
Total time to complete Offline
data collection: ( 0) seconds.
Offline data collection
capabilities: (0x53) SMART execute Offline immediate.
Auto Offline data collection on/off support.
Suspend Offline collection upon new
command.
No Offline surface scan supported.
Self-test supported.
No Conveyance Self-test supported.
Selective Self-test supported.
SMART capabilities: (0x0003) Saves SMART data before entering
power-saving mode.
Supports SMART auto save timer.
Error logging capability: (0x01) Error logging supported.
General Purpose Logging supported.
Short self-test routine
recommended polling time: ( 2) minutes.
Extended self-test routine
recommended polling time: ( 17) minutes.
SCT capabilities: (0x003d) SCT Status supported.
SCT Error Recovery Control supported.
SCT Feature Control supported.
SCT Data Table supported.
SMART Attributes Data Structure revision number: 1
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAGS VALUE WORST THRESH FAIL RAW_VALUE
1 Raw_Read_Error_Rate POSR-K 199 199 002 - 790
5 Reallocated_Sector_Ct PO--CK 099 099 010 - 48
9 Power_On_Hours -O--CK 099 099 000 - 203
12 Power_Cycle_Count -O--CK 099 099 000 - 460
170 Unknown_Attribute PO--C- 099 099 010 - 4550
171 Unknown_Attribute -O--CK 100 100 010 - 0
172 Unknown_Attribute -O--CK 100 100 010 - 0
173 Unknown_Attribute PO--C- 098 098 005 - 54
174 Unknown_Attribute -O--CK 099 099 000 - 59
183 Runtime_Bad_Block -O--CK 099 099 001 - 82
184 End-to-End_Error PO--CK 100 100 097 - 0
187 Reported_Uncorrect -O--CK 100 100 000 - 790
188 Command_Timeout -O--CK 100 100 000 - 0
190 Airflow_Temperature_Cel -O---K 079 053 000 - 21
196 Reallocated_Event_Count -O---- 099 099 000 - 48
198 Offline_Uncorrectable ----CK 099 099 000 - 3
199 UDMA_CRC_Error_Count -OSRCK 099 099 000 - 3
||||||_ K auto-keep
|||||__ C event count
||||___ R error rate
|||____ S speed/performance
||_____ O updated online
|______ P prefailure warning
General Purpose Log Directory Version 1
SMART Log Directory Version 1 [multi-sector log support]
Address Access R/W Size Description
0x00 GPL,SL R/O 1 Log Directory
0x01 GPL,SL R/O 1 Summary SMART error log
0x02 GPL,SL R/O 1 Comprehensive SMART error log
0x03 GPL,SL R/O 1 Ext. Comprehensive SMART error log
0x06 GPL,SL R/O 1 SMART self-test log
0x07 GPL,SL R/O 1 Extended self-test log
0x09 GPL,SL R/W 1 Selective self-test log
0x10 GPL,SL R/O 1 SATA NCQ Queued Error log
0x11 GPL,SL R/O 1 SATA Phy Event Counters log
0x30 GPL,SL R/O 9 IDENTIFY DEVICE data log
0x80-0x9f GPL,SL R/W 16 Host vendor specific log
0xe0 GPL,SL R/W 1 SCT Command/Status
0xe1 GPL,SL R/W 1 SCT Data Transfer
SMART Extended Comprehensive Error Log Version: 1 (1 sectors)
No Errors Logged
SMART Extended Self-test Log Version: 1 (1 sectors)
No self-tests have been logged. [To run self-tests, use: smartctl -t]
SMART Selective self-test log data structure revision number 1
SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS
1 0 0 Not_testing
2 0 0 Not_testing
3 0 0 Not_testing
4 0 0 Not_testing
5 0 0 Not_testing
255 0 65535 Read_scanning was completed without error
Selective self-test flags (0x0):
After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.
SCT Status Version: 3
SCT Version (vendor specific): 256 (0x0100)
SCT Support Level: 1
Device State: SCT command executing in background (5)
Current Temperature: 40 Celsius
Power Cycle Min/Max Temperature: 40/40 Celsius
Lifetime Min/Max Temperature: 0/70 Celsius
Under/Over Temperature Limit Count: 0/0
SCT Temperature History Version: 3 (Unknown, should be 2)
Temperature Sampling Period: 1 minute
Temperature Logging Interval: 1 minute
Min/Max recommended Temperature: 0/70 Celsius
Min/Max Temperature Limit: 0/70 Celsius
Temperature History Size (Index): 128 (0)
Index Estimated Time Temperature Celsius
1 2015-04-25 17:38 ? -
... ..(125 skipped). .. -
127 2015-04-25 19:44 ? -
0 2015-04-25 19:45 40 *********************
SCT Error Recovery Control:
Read: Disabled
Write: Disabled
Device Statistics (GP/SMART Log 0x04) not supported
SATA Phy Event Counters (GP Log 0x11)
ID Size Value Description
0x0001 2 0 Command failed due to ICRC error
0x0002 2 0 R_ERR response for data FIS
0x0003 2 0 R_ERR response for device-to-host data FIS
0x0004 2 0 R_ERR response for host-to-device data FIS
0x0005 2 0 R_ERR response for non-data FIS
0x0006 2 0 R_ERR response for device-to-host non-data FIS
0x0007 2 0 R_ERR response for host-to-device non-data FIS
0x0008 2 0 Device-to-host non-data FIS retries
0x0009 2 2 Transition from drive PhyRdy to drive PhyNRdy
0x000a 2 1 Device-to-host register FISes sent due to a COMRESET
0x000b 2 0 CRC errors within host-to-device FIS
0x000d 2 0 Non-CRC errors within host-to-device FIS
0x000f 2 0 R_ERR response for host-to-device data FIS, CRC
0x0010 2 0 R_ERR response for host-to-device data FIS, non-CRC
0x0012 2 0 R_ERR response for host-to-device non-data FIS, CRC
0x0013 2 0 R_ERR response for host-to-device non-data FIS, non-CRC