Dongle Blog

Last weekend we had to shutdown everything in the building to allow some electrical work to take place. It went pretty smoothly, although a disk failed in our scratch space file server. When I looked on Sunday evening it had stopped rebuilding with an “ECC-ERROR” in one of the other disks. I managed to coax it to rebuild onto the hot spare, and a subsequent verify cleared the error. On Monday I had a play around the failed disk to see what was wrong with it. I found an article describing how to use the SMART utils to probe a disk behind a RAID card – I hadn’t realised this was possible. Here’s the SMART data:

errol:~#smartctl -a -d 3ware,4 /dev/twa0                                                                           11:12am
smartctl version 5.36 [x86_64-redhat-linux-gnu] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF INFORMATION SECTION ===
Device Model:     ST31000340AS
Serial Number:    9QJ2BV5F
Firmware Version: SD15
User Capacity:    1,000,204,886,016 bytes
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   8
ATA Standard is:  Not recognized. Minor revision code: 0x29
Local Time is:    Mon Dec 21 11:12:49 2009 GMT
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

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:      ( 121)	The previous self-test completed having
					the read element of the test failed.
Total time to complete Offline
data collection: 		 ( 642) 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: 	 ( 227) minutes.
Conveyance self-test routine
recommended polling time: 	 (   2) minutes.

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   107   099   006    Pre-fail  Always       -       91159849
  3 Spin_Up_Time            0x0003   091   091   000    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0032   100   100   020    Old_age   Always       -       14
  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       63
  7 Seek_Error_Rate         0x000f   037   037   030    Pre-fail  Always       -       29746980996976
  9 Power_On_Hours          0x0032   089   089   000    Old_age   Always       -       9910
 10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail  Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   020    Old_age   Always       -       14
184 Unknown_Attribute       0x0032   100   100   099    Old_age   Always       -       0
187 Unknown_Attribute       0x0032   099   099   000    Old_age   Always       -       1
188 Unknown_Attribute       0x0032   100   100   000    Old_age   Always       -       0
189 Unknown_Attribute       0x003a   100   100   000    Old_age   Always       -       0
190 Unknown_Attribute       0x0022   076   066   045    Old_age   Always       -       403505176
194 Temperature_Celsius     0x0022   024   040   000    Old_age   Always       -       24 (Lifetime Min/Max 0/13)
195 Hardware_ECC_Recovered  0x001a   022   018   000    Old_age   Always       -       91159849
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       3
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age   Offline      -       3
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       0

SMART Error Log Version: 1
ATA Error Count: 1
	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 1 occurred at disk power-on lifetime: 4752 hours (198 days + 0 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 3e 8a 78 0b

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 00 80 00 8a 78 4b 00  46d+05:07:41.524  [RESERVED FOR SERIAL ATA]
  60 00 28 d8 89 78 4b 00  46d+05:07:41.522  [RESERVED FOR SERIAL ATA]
  61 00 80 80 1d de 49 00  46d+05:07:41.520  [RESERVED FOR SERIAL ATA]
  61 00 80 ff ff ff 4f 00  46d+05:07:41.514  [RESERVED FOR SERIAL ATA]
  61 00 80 ff ff ff 4f 00  46d+05:07:41.514  [RESERVED FOR SERIAL ATA]

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Short offline       Completed: read failure       90%      9910         88387051
# 2  Short offline       Completed: read failure       90%      9910         88387051
# 3  Short offline       Completed: read failure       90%      9909         88387051

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.

This is interesting – the overall health test is described as a pass, but the short test I ran is described as a fail. It’s also interesting to note that the drive only has one error logged, on startup so I’m wondering it it was just some fluke.

It appears from the SMART utils howto bad-blocks and a discussion here that the short test failure is likely to be a bad block which will be reallocated when next written to. There is a procedure for forcing this, but I’m not sure how to do this thorough the RAID controller, and anyway, I don’t really fancy having a previously rejected disk as the hot spare so I requested a replacement from the vendor.

This got me wondering – at what stage does the controller decide that a disk is “dead”? It’s pretty rare in my experience that disks just die completely, they usually start being slow, or giving read errors on particular blocks. I assume that the bad blocks can be recalculated from the RAID parity and once rewritten they will be reallocated by the disk firmware. It would be good to hear something on this from either a disk or RAID controller manufacturer but it’s hard to get through the sales stuff. In particular is it ok to reuse my failed disk. I’ll have to try to speak to someone next time I go to one of the “storage expo” type things.