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Date:      Thu, 10 Feb 2011 15:07:31 -0500
From:      Michael Powell <nightrecon@hotmail.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: Bad hard driver [SOLVED]
Message-ID:  <ij1gfu$tk6$1@dough.gmane.org>
References:  <AANLkTinWDO+8+yLuOOb7fuF2YGQpoNZ--=9cM-XbGfbm@mail.gmail.com>

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Daniel Zhelev wrote:

[snip]
> 
> The last worrying thing is the
> 
>  200 Multi_Zone_Error_Rate   0x0008   200   189   000    Old_age   Offline
>    -       3
> 
> Which according to the Internet is some mysterious value that none knows
> what it stands for, so is 3 of that mystery good?
> 

Each cylinder track has a width. A head seek is nominally supposed to 
exactly center the head over the central axis. There is some slight 
tolerance as to accidental offset, but the maximum concentration of gaussian 
magnetic domain orientation should be concentrated in the center of each 
cylinder track.

Temperature changes between cold and 'steady state' operation cause very 
small changes in the size of mechanical moving parts. A little slop factor 
will happen when read/write happens while a drive is warming up from cold. 
As long as the number remains small and doesn't change often it's probably 
nothing to worry over. If it does change a lot constantly it may be an 
indicator of worn mechanical parts. Such a thing should correlate with a 
large value of power on hours. A drive near the end of it's life may get 
wobbly head syndrome. :-)

The main consideration in both questions is a small number that maybe 
increments every once in a blue moon is nothing to become overly concerned 
with. Rather consider them a long term baseline and only become alarmed when 
they show a rather sudden and large deviation in rate of change from the 
baseline. Generally when this occurs the numbers will change in fairly 
dramatic fashion quickly and generally continue this change from that point 
on. It is this pattern you look for as a possible "pre failure" warning.

-Mike
[snip]





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