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From: carpent@coltrane.SRC.Honeywell.COM (Todd Carpenter)
Newsgroups: comp.sys.amiga
Subject: Re: Leaving Computer On - specifically hard drives
Message-ID: <20464@srcsip.UUCP>
Date: 14 Apr 89 17:54:09 GMT
References: <7684@phoenix.Princeton.EDU> <5500027@hpfcdc.HP.COM> <197qi29Ut71010MJjLg@amdahl.uts.amdahl.com>
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In-reply-to: dwl10@uts.amdahl.com's message of 14 Apr 89 14:36:22 GMT


Disk ON:

The bearings are designed to last.  I have never seen (so I'm young - big deal
- I still get around) a drive wear out due to bearings.  I'm not saying faulty
manufacturing can't produce bad bearings that wear, but that's not the same
issue.

Talking to certain drive manufacturers, the only worry they have is when the
head planes in the same place for too long (weeks/months).  The lubricant on
the disk can get a "trench" built in it, and when the head is yanked back for a
read, it can plane up, and come back down with a resounding crash.  However,
this is more than a bit unlikely, and even they don't seem too concerned by it.
If you are going to be gone a week, turn it off.  This also avoids power
problems.

If you *can* have the heads park, then sure, do so.  Good luck.  Not all drives
allow you to tell it what to do with itself.  Startup takes more time.
(though that should hardly be noticeable).

The main problem is due to power failures.  If the power is off, *most* drives
won't be affected by power surges, brown outs, etc.  If the power is on, and
the head is moving, or you are in the middle of a write, you may have a slight
problem.  If it is just sitting idle, only a major spike or power loss could
cause damage - but for power losses, the head should just retract, preventing
trouble.

Drive Off:
  Heat fluxuations are the worst for the disk, bearings, motor, and chips.
Once they are stable, very little wear occurs.  This especially apparent with
high density drives.  The servo mechanism may have a significant amount of
thermal dilation, so a "cold" drive may actually write data that it cannot read
when it is warm.

I'd leave the drive on.