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Date:      Tue, 15 Oct 1996 10:28:35 -0700 (PDT)
From:      Dave Babler <dbabler@Rigel.orionsys.com>
To:        freebsd-hardware@freebsd.org
Subject:   Re: sticky drives (was: your mail)
Message-ID:  <Pine.BSI.3.95.961015102340.20012C-100000@Rigel.orionsys.com>
In-Reply-To: <199610142244.PAA14956@GndRsh.aac.dev.com>

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On Mon, 14 Oct 1996, Rodney W. Grimes wrote:
> > On Mon, 14 Oct 1996, Rodney W. Grimes wrote:
> > 
> > > >    This is extremely dangerous, BTW.  When you take the drive out of the
> > > > freezer, condensation may form on the platters as the drive heats up.
> > > > Conversely, frost may form on the platters as the drive drops below freezing.
> > > 
> > Isn't the chamber where the platters reside hermetically sealed? If so,
> > how would moisture be there to condense in the first place? 
> 
> They are not hermetically sealed, they have a bidirection presure release
> and filter valve.  Look very closely at your disk drives.  If they did
> not do this (and the tried) the cases would blow apart when ship via
> unpressearized air freight at someplace close to 22K feet MSL.
> 

Given the normally controlled environment drives are supposed to operate
in, that makes economic sense. I am surprised that an overpressure of
10-12 psi would rupture the case, though, on a volume that small, but then
gain the castings that I've seen recently are quite thin to save material.

-Dave




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