Trying to understand some things

I'm not very technical, so I apologize in advance if what I'm asking doesn't
quite make sense.  I have a Maxtor 80GB drive that was my primary drive
until it started having data and OS corruption problems.  I ran the Maxtor
utility Powermax and the basic test indicated the drive needed advanced
testing. The advanced test indicated that the drive was failing.  I did NOT
do a Powermax low level format.  The exisiting data on the drive was
unimportant because it had been backed up, but I was hoping to "fix" the
drive in hopes of using it for occassional backups of my new WD drive, or
maybe as a scratch drive.  I ran Spinrite in level 4 on the Maxtor drive and
everything looked fine, except that two sectors were marked "U" for
unrecoverable data.  So here come my questions:

1.  I understand how Spinrite tests a drive and recovers data, but I don't
grasp what the condition of the drive is after Spinrite runs.  Is the drive
"fixed," or is it no different than it was?  I don't fully understand how
hard drive error correction works.  Am I right in thinking that all hard
drives have errors, and that the controller inside the drive keeps track of
where the bad sectors are and avoids using them?  If this is true, did
Spinrite somehow "tell"  the controller to no longer use the two sectors it
couldn't recover?  If so, the drive should now function normally unless
another sector goes bad.  But shouldn't the drive controller have detected
the problem sectors itself and stopped using them on its own?  I guess I'm
not clear on the concept.

2.  I ran the Powermax basic test after Spinrite and it now reports the
drive as being fine.   If Spinrite has"told" the drive not to use the bad
sectors, is there a chance I'll confuse it by using Powermax advanced test
again?  I haven't been able to find much info about what Powermax actually
does during its testing.  Does it somehow reset the controller, then look
for bad sectors anew (losing the info that Spinrite had provided), or does
it use the bad sector info that Spinrite provided, and thus, now ignore the
sectors which are now known to be bad, even in the more advanced tests?
Would the Powermax low level format have an effect?

Sorry for the long post, and thanks to anyone who would like to offer
information.


0
wrenchmeister
1/6/2005 10:27:21 PM
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"wrenchmeister" <wrench@motionmakersbikes.com> wrote in message
news:crke2b$rd5$1@news.grc.com...
> I don't fully understand how
> hard drive error correction works.

Modern disks keep a bunch of spare extra sectors. Now if a sector is 'bad',
this bad sector can eb taken out of service and replaced with a spare one.
Before re-allocating the bad one, SR will try to recover the data from the
bad.

> or does
> it use the bad sector info that Spinrite provided, and thus, now ignore
the
> sectors which are now known to be bad, even in the more advanced tests?

Yes, once replaced bad sectors no londer show. With a SMART tool you can
view how many sectors have been replaced.

> Would the Powermax low level format have an effect?
>

Yes, about the same, but this would be destructive to to existing data.

--
Joep


0
Joep
1/6/2005 11:36:02 PM
>Modern disks keep a bunch of spare extra sectors. Now if a sector is 'bad',
>this bad sector can eb taken out of service and replaced with a spare one.
>Before re-allocating the bad one, SR will try to recover the data from the
>bad.

>With a SMART tool you can view how many sectors have been replaced.


Thanks for the helpful info.  A few more questions:

1. What is the name of a SMART tool that can allow me to view the number of
bad sectors that are no longer in use?  I don't recall  seeing that feature
in Powermax or Spinrite.
2.  Roughly how many clusters can be replaced before the extras are used up?
3.  Does the drive, in normal functioning, ever recognize bad sectors by
itself and replace them?  Or is this something that only happens with
programs like Spinrite or low level formatting?  If the drive doesn't do it
in normal use, is that why it is recommended to run Spinrite every so often
to monitor drive health?
4.  Are bad sectors ever returned to use?  Does the SMART system ever
re-evaluate bad sectors, or are they out of use forever after they are
identified as bad the first time?

Thanks again for helping me understand.



0
wrenchmeister
1/7/2005 8:17:18 PM
"wrenchmeister" <wrench@motionmakersbikes.com> a �crit dans le message de
news:crmqqa$470$1@news.grc.com...
> >Modern disks keep a bunch of spare extra sectors. Now if a sector is
'bad',
> >this bad sector can eb taken out of service and replaced with a spare
one.
> >Before re-allocating the bad one, SR will try to recover the data from
the
> >bad.
>
> >With a SMART tool you can view how many sectors have been replaced.
>
>
> Thanks for the helpful info.  A few more questions:
>
> 1. What is the name of a SMART tool that can allow me to view the number
of
> bad sectors that are no longer in use?  I don't recall  seeing that
feature
> in Powermax or Spinrite.

I assume any SMART utility will display the margin of the relocated sectors
and the actual number of replaced ones:
SMART Monitor,
DTemp (has a small nice SMART parameter reporting tool),
list open


> 2.  Roughly how many clusters can be replaced before the extras are used
up?

Around 20 - 30 (my old Quantum lct used all 20 of clusters silently and then
start
having BADs all over the surface, even presenting a SMART error : "drive not
safe")

> 3.  Does the drive, in normal functioning, ever recognize bad sectors by
> itself and replace them?  Or is this something that only happens with
> programs like Spinrite or low level formatting?  If the drive doesn't do
it
> in normal use, is that why it is recommended to run Spinrite every so
often
> to monitor drive health?

that is the very job of SMART: among others, detecting and replacing bad
sectors, looking at the
temperature and shutting the drive down when hot, calibrating some
parameters...
see SMART documentation of the drive, since there is no universal starndard
for
all drives, each producer adds some functions to his SMART drives

> 4.  Are bad sectors ever returned to use?  Does the SMART system ever
> re-evaluate bad sectors, or are they out of use forever after they are
> identified as bad the first time?
>
they may be returned to normal use by low-level drive formatting, but this
is
highly dangerous, as the once bad sectors have a magnetical weakness that
may
show now and then, or may be permanent, you (and the drive) cannot trust
them
anymore and want to have them excluded from usage. there may be a momentary
bad status and when reformatting you may observe that the bad sector
disappeared,
but it may loss its full properties in the future, so the best is to exclude
a few to a hundred
bd sectors and have a functional drive, rather than havinga "clean" surface
and
then slowly start raining with bads... :-)

> Thanks again for helping me understand.
>

np
advise open

>


0
dark
1/10/2005 8:37:09 AM
"dark" <dnaorskpsatmar@home.ro> wrote in message
news:crten6$887$1@news.grc.com...
>
> I assume any SMART utility will display the margin of the relocated
sectors
> and the actual number of replaced ones:

Just the replaced ones.

>
>
> > 2.  Roughly how many clusters can be replaced before the extras are used
> up?
>
> Around 20 - 30 (my old Quantum lct used all 20 of clusters silently and
then
> start
> having BADs all over the surface, even presenting a SMART error : "drive
not
> safe")

It's not clusters that are replaced but sectors. On modern disks there's
100's of spare sectors.

>
> > 3.  Does the drive, in normal functioning, ever recognize bad sectors by
> > itself and replace them?

Yes, they will:

Error on read that can be corrected: Hard disks apply multiple strategies
for correcting 'bad' data allowing the disk to provide you with your data
even if a sector could not be read entirely. If the data in a sector can be
recovered using this strategy, the data is copied to a spare sector and the
bad sector is taken out of service. If an error on read could not be
corrected: If a sector can not be read and the automatic error correction
can not recover the data in the sector, the sector will become a candidate
for reallocation. A read error will be reported. The candidate for
reallocation will be reallocated when the sector is written to. Error on
write: The bad sector is taken out of service and the data is immediately
written to a spare sector. In other words, the bad sector is 'reallocated'.

  Or is this something that only happens with
> > programs like Spinrite or low level formatting?  If the drive doesn't do
> it
> > in normal use, is that why it is recommended to run Spinrite every so
> often
> > to monitor drive health?

Cause each and every sector is tested. During normal use it may take years
before a 'bad' sector is deteted. Also SR tests sectors with different bit
patterns, it may consider a sector 'weak' while the disk firmware doesn't.

>
> that is the very job of SMART: among others, detecting and replacing bad
> sectors, looking at the
> temperature and shutting the drive down when hot, calibrating some
> parameters...
> see SMART documentation of the drive, since there is no universal
starndard
> for
> all drives, each producer adds some functions to his SMART drives
>

Well, most disks at least report basic smart attributes. The non standard is
setting the thresholds, this is done by the manufacturer.

> > 4.  Are bad sectors ever returned to use?

No.

--
Joep



0
Joep
1/10/2005 8:09:56 PM
> > > 3.  Does the drive, in normal functioning, ever recognize bad sectors
by
> > > itself and replace them?
>
> Yes, they will:
>
> Error on read that can be corrected: Hard disks apply multiple strategies
> for correcting 'bad' data allowing the disk to provide you with your data
> even if a sector could not be read entirely. If the data in a sector can
be
> recovered using this strategy, the data is copied to a spare sector and
the
> bad sector is taken out of service. If an error on read could not be
> corrected: If a sector can not be read and the automatic error correction
> can not recover the data in the sector, the sector will become a candidate
> for reallocation. A read error will be reported. The candidate for
> reallocation will be reallocated when the sector is written to. Error on
> write: The bad sector is taken out of service and the data is immediately
> written to a spare sector. In other words, the bad sector is
'reallocated'.

Thanks for all the good info.  My confusion is this:  Why did my drive have
repeated corruption problems (lost data and two OS install failures) if the
SMART system should have caught the bad sectors automatically and
reallocated them?  Is there a setting that I have failed to enable?  Also,
why did Powermax describe the drive as failing, when Spinrite only found two
bad sectors?  Shouldn't Powermax have reallocated them, even though the
drive failed to do so under normal use?



0
wrenchmeister
1/11/2005 8:29:28 PM
"wrenchmeister" <wrench@motionmakersbikes.com> wrote in message
news:cs1d0t$13mi$1@news.grc.com...
>
> Thanks for all the good info.  My confusion is this:  Why did my drive
have
> repeated corruption problems (lost data and two OS install failures) if
the
> SMART system should have caught the bad sectors automatically and
> reallocated them?  Is there a setting that I have failed to enable?  Also,
> why did Powermax describe the drive as failing, when Spinrite only found
two
> bad sectors?  Shouldn't Powermax have reallocated them, even though the
> drive failed to do so under normal use?
>

Maybe new bads develop rapidly. At some point spares are all used and this
is when smart errors will be thrown at you. You really should have a look at
the drive with SMARTUDM.

--
Joep


0
Joep
1/11/2005 9:52:16 PM
Reply: