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List:       smartmontools-support
Subject:    Re: [smartmontools-support] A little help with interpreting results
From:       Franc Zabkar <fzabkar () internode ! on ! net>
Date:       2009-11-02 9:47:29
Message-ID: 1257155249_13716 () mail ! internode ! on ! net
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At 06:47 PM 2/11/09, you wrote:

>Model Family:     Western Digital Caviar SE family
>Device Model:     WDC WD2500AAJB-00J3A0
>
>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
>-       166
>   5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always
>-       0
>196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always
>-       0
>197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always
>-       4
>198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline
>-       4
>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
>-       1
>
>============================================================================
>
>With respect to value 5 Reallocated Sector Count. The normalised values
>(200) have not dropped below threshold - this means it passed on this
>attribute?

Yes

>Reallocated sector count raw value is zero, so I assume no sector have been
>reallocated?

True

>Can anyone interpret (I know its vendor specific) of Raw Read Error rate
>(166)? The normalised values haven't changed?

Sorry, don't know.

>Shouldn't bad blocks and SMART data correlate? Badblocks shows a 124
>badblocks (its a NTFS system so it was run with -b 512) - this value is of
>course very different to Offline Uncorrectable (4)?
>
>Finally windows partition table doctor lists only 4 bad sectors (which does
>tally with offline uncorrectable). By why doesn't this tally with bad
>blocks?

Windows uses a file system unit called a "cluster". A cluster is a 
group of sectors. When one sector in a cluster is bad, the entire 
cluster is marked as bad by the OS. However, the drive has no 
knowledge of clusters -- it only deals with sectors or LBAs.

In your case the cluster size appears to be 4KB, ie eight 512-byte sectors.

>The 4 sector numbers listed by partition table doctor are: 71574125 ;
>6358767 ; 1967364 ; 1551405 - what I don't get is why badblocks lists these
>numbers and more imeediately either side? (see full list of badblocks output
>below)

I don't know why the first group consists of 12 clusters rather than 
1, but I suspect that the leading sector/block of each cluster is 
some kind of index. Someone who understands NTFS will no doubt 
correct my ignorance here.

>Badblocks output

>1551360
>1551400 - 1551495 (12 clusters)

>1967352
>1967360 - 1967367 (1 cluster)

>6358712
>6358760 - 6358767 (1 cluster)

>71574112
>71574120 - 71574127 (1 cluster)

If the 4 bad sectors were caused by bad writes, which in turn were 
the result of power supply hiccups, then these "soft" errors will be 
corrected when new data are written to these sectors. Sectors which 
are marked as "pending reallocation" are always retested by the 
drive. If they pass, then they are returned to service, otherwise 
they are retired and replaced with spares.

-Franc


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