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From: desj@brahms.BERKELEY.EDU (David desJardins)
Newsgroups: net.micro,net.micro.pc
Subject: Re: "Parking" the heads on hard disks
Message-ID: <11520@ucbvax.berkeley.edu.BERKELEY.EDU>
Date: Thu, 23-Jan-86 21:09:33 EST
Article-I.D.: ucbvax.11520
Posted: Thu Jan 23 21:09:33 1986
Date-Received: Sat, 25-Jan-86 03:38:03 EST
References: <659@isrnix.UUCP> <1322@tekgvs.UUCP> <144@sci.UUCP>
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In article <144@sci.UUCP> raymund@sci.UUCP (Raymund Galvin) writes:
>
>I don't think leaving the PC on indefinitely is a good idea. The MTBF
>of typical small hard disks is usually between 5000 and 10000 hours.
>
>This implies that a hard disk that has been powered up since 11/28/85
>is 25% along the way to a failure.  These failures are the real nasty ones - 
>where the drive needs to be replaced or repaired - not just a read error.

   This number is just that, a "*mean* time between failures."  In particular
it is based on an average pattern of usage.  Obviously a hard disk which is
just idling will be less likely to break down than one which is being used.
Most hard disk failures presumably involve the head, which should be affected
relatively little by running the drive continuously.
   On the other hand there certainly are bearings and such in the drive
mechanism which can fail even if the disk is not being accessed.  Can anyone
give us a reliable estimate of the MTBF for a drive which is on for long
periods but is accessed relatively rarely?  This should also be of interest
to BBS operators, etc.

   -- David desJardins