[rescue] Bad Sectors

Mark Brown sunrescue at marknmel.com
Fri Jan 19 21:41:17 CST 2007

Patrick Giagnocavo wrote:
> On Jan 19, 2007, at 9:29 PM, Curtis H. Wilbar Jr. wrote:
>> self tests are only a small part of smart... it sounds like your just
>> getting the
>> driver 'power on' self test report... since they spin up and can see 
>> the
>> media
>> they 'pass'.  You want to look at error count reports, and any 'event
>> log' type
>> data that might be in there.  Watch out for seek errors.... those spell
>> trouble...
>> (IMHO)
> I had a 200GB WDC drive that was being monitored by the Linux 
> "smartctl" tools.  It would report threshold changes ... every hour or 
> so!  Yet it ran without losing data for many months, until I retired 
> the server it was in.
> I think that it would make sense to pay for the best IDE drive utility 
> a person could find, if you are making a good/bad decision on 
> potentially thousands of dollars worth of drives...
> --Patrick
I think all the advise so far is great! - I'll jump in here...

It has been my experience to run the vendor specific diagnostic/tools 
software for each disk, and "Low Level Format " them.  I think that a 
low level format on recent IDE disks is simply an exercise for testing 
read/write for each block, and if failure - remap the bad block. (my 
opinion here may be different than reality...;-) )

Usually I run the drive utility as follows:
- a couple of times to capture all bad blocks
- cool down the disk - turn it off - come back the next day....
- a couple of times to capture all bad blocks if any.
- a couple of times that return clean. 
If the defect list is growing rather than stabilizing., it would be 
inversely proportional to my confidence level for that disk....

Then I do a format/newfs/mount them, and untar the perl source code a 
whole bunch of times in to a whole bunch of directories.  Do dircmp from 
a known good reference copy, rinse, lather, repeat.  I would probably 
use Solaris 9 for this, with a current patch set. I use the same method 
for UFS testing. I'd rather not talk about that though, I've seen too 
many UFS bugs.....

I have had some 20gb and 80gb disks that are doing quite well now (and 
some that are still screwed). 

Mind you, I don't think they are doing any tasks that are "server" 
related.  They are living life as disks for Windows boxen, and on a test 
Solaris Nevada x86/Athlon that I have been tinkering with.

If you take the time to back up your data to tape, and you wish to 
assume the risk of these disks if they fail 1 week or 1 year from now - 
they may turn out to be perfectly serviceable.

Good luck with your rescue!


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