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Ubuntu 17.04; ext4 filesystem on 4TB WD green SATA [WDC WD40EZRX-22SPEB0]

Mount (on startup, from fstab) failed with bad superblock. fsck reported / inode damaged, but repaired it. 99% of files restored (the few that are lost are available in backup). Repaired volume mounts and operates normally.

Looking at the SMART data, I think the disk is okay. The "extended" smartctl test passed. The data is already backed up (and it's not mission critical). I already have a replacement drive. It's tempting to take a "zero tolerance" policy and replace the disk now, but as it's a £100 item, and I don't want to be chucking a wobbly and binning every disk that ever writes a bad block once.

Here's the smartctl dump. Is the disk actually dying, or did it just have a one-time mishap?

ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       61
  3 Spin_Up_Time            0x0027   195   176   021    Pre-fail  Always       -       7225
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       770
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   200   200   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   084   084   000    Old_age   Always       -       12325
 10 Spin_Retry_Count        0x0032   100   100   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   100   100   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       730
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       40
193 Load_Cycle_Count        0x0032   194   194   000    Old_age   Always       -       18613
194 Temperature_Celsius     0x0022   121   106   000    Old_age   Always       -       31
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       21

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed without error       00%     12320         -
# 2  Short offline       Completed without error       00%     12311         -

migrated from serverfault.com Oct 6 '17 at 9:15

This question came from our site for system and network administrators.

  • 1
    Looking at your smart data the disk looks like dying, but then again some attributes don't make sense. F.i. 194: is the temperature of this disk really 121C? For reference, silicon circuits start having trouble over ~95C. – Satō Katsura Oct 6 '17 at 9:23
  • @SatōKatsura that one is the raw value, i.e. 31C – roaima Oct 6 '17 at 9:34
2

According to the SMART readings, the disk seems fine at the moment.

The exciting ones for disk sectors are these

  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -    0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -    0
198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -    0

A reallocated sector is one that failed a write and was remapped elsewhere on the disk. A small number of these is acceptable. Zero is excellent.

The current pending sector value is the number of sectors that are waiting to be reallocated elsewhere. (The read failed but the disk is waiting for a write request, which is the point at which the sector gets remapped.) This may become non-zero for a while, and as the sectors get overwritten this number will decrease and the reallocated sector count will increase.

The count of offline uncorrectable sectors is the number of sectors that failed and could not be remapped. A non-zero value is bad news because it means you are losing data. Your zero value is just fine.

These next group show the duration of use of your disk drive

  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -    770
  9 Power_On_Hours          0x0032   084   084   000    Old_age   Always       -    12325
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -    730

You've had the device running for 12325 hours (if that's continuous time it's about 18 months) and during that time it has powered up and down 730 times. If you power it off daily then you've had the disk running for about 16 hours/day over two years.

Finally, it would be worth scheduling a full test every week. You can do this with a command such as smartctl -t full /dev/sda. Errors in the tests can become cause for concern.

# 1  Extended offline    Completed without error       00%     12320         -
# 2  Short offline       Completed without error       00%     12311         -

If you are using this in a NAS I would recommend a NAS grade disk. Personally I find the WD Red are very good in this respect. The cost is a little higher but the warranty is longer.

  • I think I've been spending too much effort in trying to ascribe meaning from the VALUE parameter. It seems all one can really say is that if VALUE>THRESH, the disk is probably okay. Which is effectively what the man page for smartctl says. I wasn't putting any weight on RAW_VALUE, even though - as your answer illustrates - it's often the meaningful thing. Given the labour cost of restoring such titanic disks, even from a good backup, the incremental cost of the Red disks does seem like an astute investment. Thank you very much for your excellent answer. – Finlay McWalter Oct 6 '17 at 20:29

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