[plug] Using a HDD with Badsectors

[Adrian Chadd]

On Sun, Nov 26, 2006, Timothy White wrote:
> I have a 80Gb HDD from my sisters computer, that had developed some
> bad sectors (2-4). It was undecided the reason for them developing was
> the lack of cooling in the case it was at, and the high temperatures
> it had reached.
> I replaced her HDD, and not wanting to waste 80Gb of almost goodness,
> I was wondering the best way to use it. After installing Ubuntu, I did
> a "fsck.ext3 -c -c" which found 2 bad blocks. But I'm still getting a
> few error messages in the logs.

HDD's do a few things automagically: one of the things it'll do is try
to map bad sectors to "spare" sectors located in various spots on the disk.
It'll try to re-read the data from the dodgy sector and write it to the
new sector; and if it fails it'll return a read error and mark the sector
invalid.

Hopefully at -that- point you can write data to that sector; it'll then
write data for that sector to the newly-remapped spare sector (which
isn't spare now!) and you shouldn't have any trouble.

> After seeing this, I installed smartmontools, and made sure SMART was
> enabled on the drive, as well as setting up daily and weekly SMART
> tests.

You should check the ongoing temperature and compare error rates to
"corrected" rates. Also, check the relocated sector count:

On the disk below which is failing:

  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       24

On the disk next to it which isn't failing:

  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       0

You're stuck when you run out of spare sectors to reallocate into. ;)

> So far, I've gotten 3 emails from smartmon with the following messages.
> 
> Device: /dev/sda, 1 Currently unreadable (pending) sectors
> Device: /dev/sda, 1 Offline uncorrectable sectors
> Device: /dev/sda, Self-Test Log error count increased from 0 to 1

Thats the disk trying to read the data from that bad sector; hopefully
into a spare sector.

> The last message to me looks like one I can ignore, as I have
> scheduled Self-Tests. Do I need to worry about the other 2, if I've
> run badblocks via fsck?

> locate the blocks, and repartition so no filesystems cross the bad
> blocks area. I'm fairly sure they are located together.

Modern HDD's, unfortuately, don't neatly map physical layout to your logical
partition layout - so you might have luck or you might not have luck.
Just run the badblocks test and see what else is picked up.

And, TBH, Netplus are doing 80gig PATA disks for $58. :) I'd suggest just
replacing it and making sure you're setup some better cooling for next time.
My current (old!) favourite tower case has a pair of fans in front of the
HDD array and a pair of fans behind the HDD array. Very pretty!

Just for Linux HDD fun:

(lots of errors on hda, which I'm about to replace..)
hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
hda: dma_intr: error=0x40 { UncorrectableError }, LBAsect=156114223, sector=156114097
ide: failed opcode was: unknown
end_request: I/O error, dev hda, sector 156114097
md: md1: sync done.
RAID1 conf printout:
 --- wd:2 rd:2
 disk 0, wo:0, o:1, dev:hda2
 disk 1, wo:0, o:1, dev:hdc2
[root at hosting-test ~]# cat /proc/mdstat
Personalities : [raid1] 
md0 : active raid1 hdc1[1] hda1[0]
      521984 blocks [2/2] [UU]
      
md1 : active raid1 hdc2[1] hda2[0]
      77625984 blocks [2/2] [UU]
      
Thanks Linux, for not degrading my software raid1 and telling me that i need
to damned look at the failed disk. I hope the array doesn't fail before I've
replaced hda! :) I'm glad I learnt this particular behaviour early on.


Adrian





- Xenion - http://www.xenion.com.au/ - Hosting and Commercial Squid Support -