Disk errors

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UDMA mode

I ran into a problem booting an embedded Linux system where the kernel log would show failed attempts to set UDMA mode on an IDE Solid State Drive. It would start with UDMA/44 then try UDMA/33, UDMA/25, UDMA/16, and eventually end up in PIO mode with no DMA selected.

The problem turned out to be a faulty setup of the RAM and configuration of the DMA controller in the embedded SOC. There were a number of bad things happening. First, the version of the SOC chip we were using had bad cache coherency and DMA bus arbitration problems. Second, our memory map layout in the bootloader didn't match the layout of the Linux Kernel -- this caused some weird problems! If a network cable was plugged into the device during boot and a packet came in just as the boot loader was switching to the kernel then it was possible for the DMA controller to put the packet data into memory that thee kernel was using for something else. This would cause all kinds of other weird problems in addition to the one below.

mpc512x_ide: fsl_ata_dma_timer_expiry hda: fifo_kill=58
fsl_dma_end:dma transfer read err.
hda: lost interrupt
hda: dma_intr: status=0x59 { DriveReady SeekComplete DataRequest Error }
hda: dma_intr: error=0x84 <3>{ DriveStatusError BadCRC }
ide: failed opocode was: unknown
hda: UDMA/16 mode selected
__fsl_ata_resetproc: resetting ATA controller
ide0: reset: success
mpc512x_ide: fsl_ata_dma_timer_expiry hda: fifo_kill=58
fsl_dma_end:dma transfer read err.
pending:00000000
hda: dma_intr: status=0x59 { DriveReady SeekComplete DataRequest Error }
hda: dma_intr: error=0x84 <3>{ DriveStatusError BadCRC }
ide: failed opocode was: unknown
hda: no DMA mode selected
__fsl_ata_resetproc: resetting ATA controller
hda: drive not ready for command
ide0: reset: success

Smartmon

Smartmon isn't always easy to understand.

WORST and THRESH are a scaled value. RAW_VALUE usually makes the most sense to a human.

Here is appears that my drive got over 50 degrees C at least once in the past.

Also there have been 47 UNC errors at LBA = 0x0fffffff = 268435455. The drive only saves the most recent five errors.

But the drive also reports SMART overall-health self-assessment test result: PASSED. What does this mean? I think it means that maybe it got hot and had trouble reading part of the drive, but for whatever reason the drive doesn't think this is a permanently bad situation.

Also, it's strange that it reports Error: UNC at LBA = 0x0fffffff = 268435455. I'm sure LBA=0x0fffffff is not a real block. Perhaps some piece of software requested the drive read from this block and the drive got confused, but rather than report back to the client that the read request was invalid the drive got confused and registered this as a physical error. Firmware bug?

I read that UNC errors can have soft causes. In other words, the ECC code may have failed, but that does not necessarily mean you have a hardware problem. It may indicate a power loss where the drive was unable to finish a block. An `fsck` may show a filesystem error that corresponds to the LBA of the error.

One thing I've noticed from searching the web is that many people are alarmist and reactionary when it comes to analyzing these reports. For instance, some people want to see 'Hardware_ECC_Recovered' show zero errors even though the value may well be within spec and this attribute shows the error was recovered after all! All drives always have errors at some level. Another funny one is the Seek_Error_Rate (Attribute ID# 7) RAW_VALUE which is always going up. It actually goes up pretty fast -- more than 1 a second. People often freak out over this even though this is the raw value, not the normalized value. The 'WHEN_FAILED' attribute doesn't even show that the drive has failed this parameter.

Still, I think I'll test my backups and run `fsck`.

# smartctl --all /dev/sda
smartctl version 5.38 [i686-pc-linux-gnu] Copyright (C) 2002-8 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF INFORMATION SECTION ===
Device Model:     ST9320421AS
Serial Number:    5TJ09W81
Firmware Version: SD13
User Capacity:    320,072,933,376 bytes
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   8
ATA Standard is:  ATA-8-ACS revision 4
Local Time is:    Tue Feb 23 00:27:07 2010 PST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
See vendor-specific Attribute list for marginal Attributes.

General SMART Values:
Offline data collection status:  (0x82) Offline data collection activity
                                        was completed without error.
                                        Auto Offline Data Collection: Enabled.
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:                    (0x7b) SMART execute Offline immediate.
                                        Auto Offline data collection on/off support.
                                        Suspend Offline collection upon new
                                        command.
                                        Offline surface scan supported.
                                        Self-test supported.
                                        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:        (   1) minutes.
Extended self-test routine
recommended polling time:        (  95) minutes.
Conveyance self-test routine
recommended polling time:        (   2) minutes.
SCT capabilities:              (0x103b) SCT Status supported.
                                        SCT Feature Control supported.
                                        SCT Data Table supported.

SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   115   098   006    Pre-fail  Always       -       97873865
  3 Spin_Up_Time            0x0003   098   097   000    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0032   099   099   020    Old_age   Always       -       1838
  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       6
  7 Seek_Error_Rate         0x000f   079   060   030    Pre-fail  Always       -       4385869775
  9 Power_On_Hours          0x0032   090   090   000    Old_age   Always       -       9458
 10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail  Always       -       1
 12 Power_Cycle_Count       0x0032   100   037   020    Old_age   Always       -       134
184 Unknown_Attribute       0x0032   100   100   099    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   053   053   000    Old_age   Always       -       47
188 Unknown_Attribute       0x0032   100   100   000    Old_age   Always       -       6
189 High_Fly_Writes         0x003a   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0022   051   045   045    Old_age   Always   In_the_past 49 (Lifetime Min/Max 23/52)
191 G-Sense_Error_Rate      0x0032   100   100   000    Old_age   Always       -       0
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       14
193 Load_Cycle_Count        0x0032   068   068   000    Old_age   Always       -       64826
194 Temperature_Celsius     0x0022   049   055   000    Old_age   Always       -       49 (0 20 0 0)
195 Hardware_ECC_Recovered  0x001a   047   035   000    Old_age   Always       -       97873865
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       0
254 Unknown_Attribute       0x0032   100   100   000    Old_age   Always       -       0

SMART Error Log Version: 1
ATA Error Count: 47 (device log contains only the most recent five errors)
        CR = Command Register [HEX]
        FR = Features Register [HEX]
        SC = Sector Count Register [HEX]
        SN = Sector Number Register [HEX]
        CL = Cylinder Low Register [HEX]
        CH = Cylinder High Register [HEX]
        DH = Device/Head Register [HEX]
        DC = Device Command Register [HEX]
        ER = Error register [HEX]
        ST = Status register [HEX]
Powered_Up_Time is measured from power on, and printed as
DDd+hh:mm:SS.sss where DD=days, hh=hours, mm=minutes,
SS=sec, and sss=millisec. It "wraps" after 49.710 days.

Error 47 occurred at disk power-on lifetime: 9062 hours (377 days + 14 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  25 00 08 ff ff ff ef 00      00:10:58.846  READ DMA EXT
  27 00 00 00 00 00 e0 00      00:10:58.815  READ NATIVE MAX ADDRESS EXT
  ec 00 00 00 00 00 a0 00      00:10:58.806  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 00      00:10:58.783  SET FEATURES [Set transfer mode]
  27 00 00 00 00 00 e0 00      00:10:58.731  READ NATIVE MAX ADDRESS EXT

Error 46 occurred at disk power-on lifetime: 9062 hours (377 days + 14 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  25 00 08 ff ff ff ef 00      00:10:55.878  READ DMA EXT
  27 00 00 00 00 00 e0 00      00:10:55.847  READ NATIVE MAX ADDRESS EXT
  ec 00 00 00 00 00 a0 00      00:10:55.839  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 00      00:10:55.818  SET FEATURES [Set transfer mode]
  27 00 00 00 00 00 e0 00      00:10:55.763  READ NATIVE MAX ADDRESS EXT

Error 45 occurred at disk power-on lifetime: 9062 hours (377 days + 14 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  25 00 08 ff ff ff ef 00      00:10:52.855  READ DMA EXT
  27 00 00 00 00 00 e0 00      00:10:52.823  READ NATIVE MAX ADDRESS EXT
  ec 00 00 00 00 00 a0 00      00:10:52.815  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 00      00:10:52.792  SET FEATURES [Set transfer mode]
  27 00 00 00 00 00 e0 00      00:10:52.739  READ NATIVE MAX ADDRESS EXT

Error 44 occurred at disk power-on lifetime: 9062 hours (377 days + 14 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  25 00 08 ff ff ff ef 00      00:10:49.947  READ DMA EXT
  27 00 00 00 00 00 e0 00      00:10:49.916  READ NATIVE MAX ADDRESS EXT
  ec 00 00 00 00 00 a0 00      00:10:49.907  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 00      00:10:49.886  SET FEATURES [Set transfer mode]
  27 00 00 00 00 00 e0 00      00:10:49.832  READ NATIVE MAX ADDRESS EXT

Error 43 occurred at disk power-on lifetime: 9062 hours (377 days + 14 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  25 00 08 ff ff ff ef 00      00:10:47.031  READ DMA EXT
  27 00 00 00 00 00 e0 00      00:10:47.000  READ NATIVE MAX ADDRESS EXT
  ec 00 00 00 00 00 a0 00      00:10:46.992  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 00      00:10:46.970  SET FEATURES [Set transfer mode]
  27 00 00 00 00 00 e0 00      00:10:46.912  READ NATIVE MAX ADDRESS EXT

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Short offline       Completed without error       00%      9458         -
# 2  Short offline       Completed without error       00%         0         -

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
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.