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From: Paul.Heller@f421.n109.z1.fidonet.org (Paul Heller)
Newsgroups: comp.sys.mac.hardware
Subject: Re:  Leaving Mac On
Message-ID: <3454.27BD10C0@blkcat.fidonet.org>
Date: 16 Feb 91 03:41:53 GMT
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Organization: FidoNet node 1:109/421 - The Twilight Clone, Paul Heller
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WC> The most cogent reason I've seen for turning off the mac is the possib
WC> of excessive wear on the spinning hard drive.  How well engineered are
WC> hard drives in that regard?  How many spin hours can they be expected 
WC> last?  Lastly, is it feasible to create a "sleep" mode for your comput
WC> in which the hard drive spins down but the CPU stays on to keep warm?
 
There is a school of thought that believes that hard drives last longer
if you leave them running around the clock, for several reasons: 
 
  a) there's no temperature cycling.  Hard drives generate a fair
     amount of heat, and daily heating up & cooling down is believed
     by some to contribute to wear and tear.  Also, heating & cooling
     may, so goes the theory, cause air to be breathed in & out,
     possibly carrying contaminants.  
 
  b) Electrical surges during startup are less frequent.  This applies
     to the rest of the computer as well.
 
  c) In designs where the read/write heads come to rest on the disk
     surfaces, keeping the drive spinning reduces the chance that the
     heads & media surface will do nasty things to each other while
     at rest (or while bumped while at rest.
 
Personally, I'm inclined to believe that the period when a computer is
powered up from a cold start is a relatively stressful time for the
components -- all of them, not just the hard drive -- and that the
strategy of keeping the equipment running around the clock has
something going for it.  When a computer or hard disk fails, more often
than not it's when it's first turned on ... the downside of this
strategy is that power cost isn't insignificant, and leaving a computer
running that draws, say, 150 watts, for 16 unnecessary hours a day
might increase your power bill by $10 or $11 per month, or $120 or so
per year.  
 
As far as the bearings in the drives are concerned, the ones produced
during the past few years all seem to have very long lives, and I doubt
that having them spin 24 hours/day is going to cause them to fail
prematurely because the bearings wear out.
 
This is probably one of those can't-win situations.  My advice:  buy
good-quality components and keep your fingers crossed.


--  

        Paul Heller, Paul.Heller@f421.n109.z1.fidonet.org
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