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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Disk drive handling in assembly
References: <3D9CF7A9.BF4BB1C0@webaccess.net> <email@example.com> <3D9D1517.F9300485@webaccess.net>
Date: Fri, 04 Oct 2002 13:48:02 GMT
NNTP-Posting-Date: Fri, 04 Oct 2002 06:48:02 PDT
> Chuck Simmons wrote in message news:<3D9D1517.F9300485@webaccess.net>...
> > The little lost angel wrote:
> > >
> > > On Fri, 04 Oct 2002 02:06:54 GMT, Chuck Simmons
> > > wrote:
> > > >day. The motive for this question derives from a question about high
> > > >failure rate experienced by a particular company. I have already given
> > > IBM?? :D
> > No. Nobody at IBM ever asks me anything. That's probably wise of them.
> > > >Does the final product provide for appropriate cooling air for the head
> > > >disk assembly and the electronics board mounted to the head disk
> > > >assembly?
> > > Could it be the environment the HDD are used in?
> > I was asked to consider this issue because I have 20 years experience in
> > the hard drive business. Since, at this point, the whole thing is a
> > favor for an old friend, I consulted another hard drive engineer with 30
> > years experience who I know. We independently concluded that the most
> > probable problem is handling and probably hard work surfaces or forcing
> > drives into mounts with tools. Both guarantee high failure rates at
> > least in our combined experience at several companies spanning a lot of
> > disk drive history. ESD is probably second to mechanical abuse as a
> > cause of high failure rates. I put environment at the bottom of the
> > list, in this case, because the statistics do not deviate with geography
> > (wide spread sites).
> > My questions are in top to bottom order of likelyhood of causing field
> > failures at a moderate but constant rate.
> > Chuck
> After spending many years assembling computers and servicing returns,
> there are several factors I noticed over the years. The odd time, bad
> drives came in batches as was the case some years ago with a large lot
> of Compac machines and Quantum hard drives. Some various products may
> actually be grey market components which I also saw a lot of. Some
> manufacturers products were simply better than others, and I
> experienced a higher failure rate with certain manufacturers,
> especially if it was a newer capacity drive. Then came the matter of
> drive mounting. If the bays were somewhat too large where the drives
> mounting screws forced the body outwards then you could have problems
> later on. If the mounting screws were too long then the screw might
> butt up against a circuit board inside or something similar, this
> could cause the death of a lot of drives. Drives should be handled
> with some attention to ESD prior to installing in the case and some
> care should also be taken when attaching or removing cabling. Cabling
> (power/data) should also not put any undue stress on the drive. This
> can be accomplished by putting a short bend a few inches out from
> where the cabling connects to the drive. Cable ties also help to
> reduce cabling vibration on the drive, especially if the computer is
> being moved around quite a bit. Finally, as a general rule of thumb,
> do not mount the drives up side down.
That's one or two drives per box type handling rather than hot swap
storage system handling. Mounting is not what I like in the application
in that the drives are mounted with Velcro to facilitate rapid hot swap
repair (yes, storage systems require hot swap or you might as well not
I didn't ask which way up the drives are mounted. I never heard of any
sensitivity to that when there is forced air cooling. I can't think of
anything inside of a head disk assembly that has any orientation
sensitivity. All of the bearings are dead loaded and up heads and down
heads refers to gimble orientation rather than load direction unless
that has changed. The other engineer considering this issue is a
mechanical engineer and he didn't ask about orientation either. Do you
have evidence that it matters?
As it happens, I probably know some of the people who designed these
drives since I think I know where they were designed (brand and type
give me a big clue that the drives are probably not Silicon Valley,
Irvine CA or Shrewsbury MA designs).
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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