Defining Disk Image Dump Standard

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Wed May 31 09:02:13 2000

> package, but the failure rate of FD's is on the order of a part in 10^9 or
> so. The random failure rate of a SCSI interface has been claimed to be a
> part in 10^15, and I'd bet the random failure rate of a plastic packaged

You babbling. Disk failure rates are in bits read. Eprom failure rates
are in device hours. Typical failure rate for plastic eproms is 300-500
failures (hard) in 10^9! So the more eproms you have for a given period
of time the more likely the failure.

Also while device life is long the assumptions that it is constant over
life are not true, nor is the life infinate.

> It's for that reason that I think all this effort put into magnetic storage
> for an archive that will, hopefully outlive its creators, is a mite unwise.

Magnetic storage is proven, while it has a finite shelf life it's well
understood and can be prolonged. Linear mag tape is likely the most
reliable of all.

OTP eproms are barely 20 years old and NOT considered a lifetime media nor
an economical one.


Allison



>
> Dick
>
> ----- Original Message -----
> From: allisonp <allisonp_at_world.std.com>
> To: <classiccmp_at_classiccmp.org>
> Sent: Tuesday, May 30, 2000 6:28 PM
> Subject: Re: Defining Disk Image Dump Standard
>
>
> > >If you're serious about creating an archive. It needs to be permanent,
> so
> > >it's essentially requisite that the media be write-once. I'd say you're
> > >better off with an OTP EPROM. Hardware to create them is dirt-simple to
> > >create, eraseable/rewritable equivalents are readily available, and even
> if
> > >the OTP's (very inexpensive, by the way) become scarce, there will still
> be
> > >rewritables available which can be write protected by removing the VPP or
> > >program pin. Use those and you'll have a real archive. What's more,
> there
> > >are no mechanical components, nothing to rust, become misaligned, or wear
> > >out.
> >
> >
> > Your kidding? Right? Eproms, have a finite random failure rate and while
> > better
> > in some ways over time you still run the risk of total failure due to:
> >
> > Environment, humidity increases failure rate.
> > Temperature
> > Time
> > Electrical stress.
> >
> > This does not include ESD and circuit mishandling. it still assumes
> > compatable technology (try reading a ECL prom using TTL).
> >
> > Add to this the great number of devices needed to contain said archive
> > your risking the boat in exactly the same way as CDrom or on shorter
> > time spans magnetic media.
> >
> > All of this is seperate from the format that will assure recovery of the
> > data.
> >
> > Myself I'd rather risk even floppies with their known weakness and use
> > redundant recording and added error detection/correction. Even when
> > applied to CDroms this is more viable.
> >
> > Most of all it matters not what you do, what you do it on! It does matter
> > that sufficient data on what was done is available along with the archive
> > to reconstruct not only the data but the systems that archived it (or can
> > recover it!!!). Books work because they can be preserved and copied
> > if they start to decompose and we teach the languges needed to read
> > them.
> >
> > Reminds me of an old theological arguement of how many angles can
> > dance on the head of a pin. Untill we have music, a pin and angles
> > it's simply an exercise with a meaningless outcome to all but the
> faithful.
> >
> > Allison
> >
>
Received on Wed May 31 2000 - 09:02:13 BST