I have a brand new IDE drive (250GB Maxtor) that has a sector
that consistently triggers a CRC error on read. I find this
puzzling, as I thought IDE disks were supposed to automatically
remap bad sectors. And always have in my past experience.

However, this is not the first time that I come across IDE disks
that don't remap in the past few years. Can someone clue me in
as to what's happening ?

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"Finally I am becoming stupider no more." -- Paul Erdös' epitaph

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Andre Majorel  <amajorel@teezer.fr> wrote:
>I have a brand new IDE drive (250GB Maxtor) that has a sector
>that consistently triggers a CRC error on read. I find this
>puzzling, as I thought IDE disks were supposed to automatically
>remap bad sectors. And always have in my past experience.
>
>However, this is not the first time that I come across IDE disks
>that don't remap in the past few years. Can someone clue me in
>as to what's happening ?

Well, it could be that all the "spare" sectors used, if that's
happened it won't remap at all, because there's no place to remap to.

If that happens on a NEW disk, get it replaced...


Also, you're talking about CRC errors on read, remember that while
remapping on WRITE is trivial, since the data that was lost wasn't
interresting anyway (it was going to be overwritten)...

For READ it's more complicated, if it could recover the data using the
ECC codes it can just remap it and be done with it, but if the data is
lost that must be handled special somehow, the error MUST be reported
back to the upper layers, so that they know data has been lost.

It can either remap the sector immediately, but mark it as
"temporarily bad", or defer the remapping until the sector is written
the next time (marking the sector as needing remapping). In either
case it will continue to report CRC errors until the sector has been
written, since that's the only way to indicate that the real data has
been lost!

It's of course also possible to ignore the data loss and just silently
remap on unreadable sectors during read, but one could at least HOPE
that no IDE manufacturer cares that little about their customers
data! :-)

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On 2004-04-18, Torbjorn Lindgren <tl@none.none.invalid> wrote:
> Andre Majorel  <amajorel@teezer.fr> wrote: 
>
> Well, it could be that all the "spare" sectors used, if that's
> happened it won't remap at all, because there's no place to remap to.
>
> If that happens on a NEW disk, get it replaced...

This doesn't seem to be the case :

| # smartctl -a /dev/hdc
| Device Model:     Maxtor 7Y250P0
| SMART support is: Available - device has SMART capability.
| SMART support is: Enabled

| capabilities: (0x5b) SMART execute Offline immediate.
|   Auto Offline data collection on/off support.
|   Suspend Offline collection upon new command.
|   Offline surface scan supported.
|   Self-test supported.
|   No Conveyance Self-test supported.
|   Selective Self-test supported.
|
| SMART Attributes Data Structure revision number: 16
| Vendor Specific SMART Attributes with Thresholds:
| ID# ATTRIBUTE_NAME          FLAG   VAL WOR THR TYPE     UPDATED  RAW_VALUE
|   3 Spin_Up_Time            0x0027 252 252 063 Pre-fail Always   1311
|   4 Start_Stop_Count        0x0032 253 253 000 Old_age  Always   4
|   5 Reallocated_Sector_Ct   0x0033 253 253 063 Pre-fail Always   2

I'm not quite sure how to read SMART values but 253 seems to
mean "very good" or "perfect". The raw value (2) may be the
number of remapped sectors.

Is there any way to get the details of reallocated sectors from
the drive, by the way ?

|   6 Read_Channel_Margin     0x0001 253 253 100 Pre-fail Offline  0
|   7 Seek_Error_Rate         0x000a 253 252 000 Old_age  Always   0
|   8 Seek_Time_Performance   0x0027 252 251 187 Pre-fail Always   53547

Brand new :

|   9 Power_On_Minutes        0x0032 253 253 000 Old_age  Always   39h+19m

The drive seems to be in fairly good shape so far :

|  10 Spin_Retry_Count        0x002b 252 252 157 Pre-fail Always   0
|  11 Calibration_Retry_Count 0x002b 252 252 223 Pre-fail Always   0
|  12 Power_Cycle_Count       0x0032 253 253 000 Old_age  Always   6
| 192 Power-Off_Retract_Count 0x0032 253 253 000 Old_age  Always   0
| 193 Load_Cycle_Count        0x0032 253 253 000 Old_age  Always   0
| 194 Temperature_Celsius     0x0032 253 253 000 Old_age  Always   43
| 195 Hardware_ECC_Recovered  0x000a 253 252 000 Old_age  Always   12285
| 196 Reallocated_Event_Count 0x0008 253 253 000 Old_age  Offline  0
| 197 Current_Pending_Sector  0x0008 253 253 000 Old_age  Offline  2
| 198 Offline_Uncorrectable   0x0008 253 253 000 Old_age  Offline  0
| 199 UDMA_CRC_Error_Count    0x0008 199 199 000 Old_age  Offline  0
| 200 Multi_Zone_Error_Rate   0x000a 253 252 000 Old_age  Always   0
| 201 Soft_Read_Error_Rate    0x000a 253 252 000 Old_age  Always   0
| 202 TA_Increase_Count       0x000a 253 252 000 Old_age  Always   0
| 203 Run_Out_Cancel          0x000b 253 252 180 Pre-fail Always   0
| 204 Shock_Count_Write_Opern 0x000a 253 252 000 Old_age  Always   0
| 205 Shock_Rate_Write_Opern  0x000a 253 252 000 Old_age  Always   0
| 207 Spin_High_Current       0x002a 252 252 000 Old_age  Always   0
| 208 Spin_Buzz               0x002a 252 252 000 Old_age  Always   0
| 209 Offline_Seek_Performnce 0x0024 149 149 000 Old_age  Offline  0
|  99 Unknown_Attribute       0x0004 253 253 000 Old_age  Offline  0
| 100 Unknown_Attribute       0x0004 253 253 000 Old_age  Offline  0
| 101 Unknown_Attribute       0x0004 253 253 000 Old_age  Offline  0

The last five errors were uncorrectable read errors like this
one :

| Error 352 occurred at disk power-on lifetime: 22 hours
|   When the command that caused the error occurred, the device
|   was in an unknown state.
|
|   After command completion occurred, registers were:
|   ER ST SC SN CL CH DH
|   -- -- -- -- -- -- --
|   40 51 2a d6 bc 43 e0  Error: UNC 42 sectors at LBA = 0x0043bcd6 = 443925
4
|
|   Commands leading to the command that caused the error were:
|   CR FR SC SN CL CH DH DC   Timestamp  Command/Feature_Name
|   -- -- -- -- -- -- -- --   ---------  --------------------
|   25 00 2a d6 bc 43 e0 08   13047.376  READ DMA EXT
|   25 00 2c d4 bc 43 e0 08   12980.816  READ DMA EXT
|   25 00 2e d2 bc 43 e0 08   12979.792  READ DMA EXT
|   25 00 30 d0 bc 43 e0 08   12978.736  READ DMA EXT
|   25 00 32 ce bc 43 e0 08   12977.712  READ DMA EXT

> Also, you're talking about CRC errors on read, remember that while
> remapping on WRITE is trivial, since the data that was lost wasn't
> interresting anyway (it was going to be overwritten)...
>
> For READ it's more complicated, if it could recover the data using the
> ECC codes it can just remap it and be done with it, but if the data is
> lost that must be handled special somehow, the error MUST be reported
> back to the upper layers, so that they know data has been lost.
>
> It can either remap the sector immediately, but mark it as
> "temporarily bad", or defer the remapping until the sector is written
> the next time (marking the sector as needing remapping). In either
> case it will continue to report CRC errors until the sector has been
> written, since that's the only way to indicate that the real data has
> been lost!

OK, got it. Thank you.

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"Finally I am becoming stupider no more." -- Paul Erdös' epitaph

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On Fri, 16 Apr 2004 23:19:47 +0000 (UTC), Andre Majorel
<amajorel@teezer.fr> wrote:

>I have a brand new IDE drive (250GB Maxtor) that has a sector
>that consistently triggers a CRC error on read.

The file could be corrupted.  What caused that corruption is what
should worry you.  I recently had a file corruption issue, where some
files, when copied between drives, would be corrupt after being
copied.  There seemed to be no pattern whatsoever.  It turned out to
be the BIOS code going bad, and simply reflashing the BIOS solved the
issue.

A friend also had a problem with file corruption on his laptop.
Within minutes of booting from a fresh image, system files would
become corrupt and XP would BSOD.  The problem turned out to be a bad
controller board on the hard drive.  The drive was replaced.

I have and have used plenty of Maxtor drives, and the only problem I
ever had was with a drive that was spinning during the LA earthquake.
It didn't survive.  Maxtor sent a replacement fresh off the line the
next day, before I even sent the damaged drive back.  They didn't have
to cover the "act of God", but they did.

--
John DeGroof, Compressionist
DVD, DAD, DVD Audio, MPEG, AC3, DTS, PCM, DSD, MLP

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> | 197 Current_Pending_Sector  0x0008 253 253 000 Old_age  Offline  2

Andre, this is a sign of trouble.  There are two sectors on the disk
that could not be read by the operating system.
[vbcol=seagreen]
> |   40 51 2a d6 bc 43 e0  Error: UNC 42 sectors at LBA = 0x0043bcd6 = 4439254[/vbc
ol]

One of the unreadable sectors is at LBA = 0x0043bcd6 = 4439254 . It is
uncorrectable, meaning that the ECC bytes are inconsistent.

Have a look at http://smartmontools.sourceforge.net/BadBlockHowTo.txt
for some suggestions.

If you run an extended self-test '-t long' on the disk, it should fail
at these unreadable LBAs.

Bruce

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On 2004-04-19, Bruce Allen <ballen@uwm.edu> wrote:
 
>
> Andre, this is a sign of trouble.  There are two sectors on the disk
> that could not be read by the operating system.
> 
>
> One of the unreadable sectors is at LBA = 0x0043bcd6 = 4439254 . It is
> uncorrectable, meaning that the ECC bytes are inconsistent.
>
> Have a look at http://smartmontools.sourceforge.net/BadBlockHowTo.txt
> for some suggestions.

Interesting reading, thank you for the link (and for
smartmontools, too).

I used a destructive bad blocks scanner and the UNC errors went
away. Interestingly, the raw value for Reallocated_Sector_Ct is
now zero. This suggests that, after rewriting the sector, the
drive found it reliable enough to keep using it. A bit scary,
but at that price, I guess I can't complain.

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"Finally I am becoming stupider no more." -- Paul Erdös' epitaph

[ Post a follow-up to this message ]

> >> | 197 Current_Pending_Sector  0x0008 253 253 000 Old_age  Offline  2 
>
> Interesting reading, thank you for the link (and for
> smartmontools, too).

You're welcome.

> I used a destructive bad blocks scanner and the UNC errors went
> away.

Good -- problem fixed.

> Interestingly, the raw value for Reallocated_Sector_Ct is
> now zero. This suggests that, after rewriting the sector, the
> drive found it reliable enough to keep using it.

That's possible.  If the drive was powered off when the sector was
being written, that might have made it uncorrectable because it had a
corrupted ECC value written to the disk.  In which case, when the
sector is written again, the ECC code get laid down consistently and
all is well.

> A bit scary, but at that price, I guess I can't complain.

There's nothing to be scared about if you back up your data.  So don't
complain, make backups instead.

Cheers,
Bruce

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