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Re: [SLUG] Can hard disk behaviour be an indicator of a dodgy power supply



  While I can't say for sure in your instance, intermittant power fluctuations 
can produce surges in your low voltage computer power. Typically, such a 
fluctuation would need to be >0.2s, just enough for the caps in the power 
supply to partially discharge, but not enough for them to totally discharge 
(around 0.3s). As the power supply switches on again and "fills" the caps with 
current, this can produce a small spike on your 5V and 12V power rails, 
typically resetting hard drives. This reset can cause failure in the drive if 
the surge is of sufficient power or you experience a double-surge very quickly 
which resets and then resets the HDDs again before they have a chance to fully 
reset.
  If your affected hard drives are a few years old, I would expect that this is 
what has happened and, unfortunately, there is not a lot to be done. A good UPS 
will usually solve the problem.

Gnuthad

  You can quite easily kill your entire computer (literally), merely by 
flicking the power on and off 6-8 times in rapid succession. (BOFH Hint #1024)

On 17 Jun 01, at 23:24, Terry Collins wrote:

> Has anyone had any experience with a dodgy power supply killing scsi
> hard disks?
> 
> I've just rebuilt a file server a number of times as a succession of
> scsi hard disks have failed. The pattern was fairly similar.
> 
> They would become musical - the ting ting ting of the "head" hitting the
> stop, then about 24 hours later, there would be major problems with
> large numbers of bus errors then total failure. On each occassion, it
> was the first drive (/dev/sda) that failed, so this meant that Linux was
> reinstalled each time.
> 
> As the drives were all the one brand and model IBM DCAS-34330 (4Gb
> single ended) and they have been in used continuously for 4 years, I was
> inclined to think dodgy model or dodgy batch. However, I heard musical
> notes again tonight and all that remains are three drives of a different
> brand and model. At the same time, the tape drive seemed to drop power
> (which was kind of not appreciated as I was in the middle of a 20Gb
> backup off three machines) but it recovered and carried on.
> 
> So I'm wondering if my problem is really a intermittently dodgy power
> supply and asking if anyone has experienced anything similar.
> 


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