[Tig] Archiving (was Re: Holographic Drive at NAB)

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Tue Apr 22 17:36:14 BST 2008

On Mon, 21 Apr 2008, Jim Houston wrote:

> This is a poor idea.  As it turns out, hard drives have significant 
> problems from an archival standpoint that make tape a better and 
> safer medium. Among the issues are that hard drives spin on a 
> bearing that is coated with a volatile oil.  Whether you run the 
> drive or not, this oil degrades over time and can cause stickion. 
> Most drives are designed with a 3-5 year lifetime and the failure 
> curve at the beginning of their life and within months of the end of 
> the design life are very high. The built-in heads and unsealed

On its way to the list, this email will pass through a disk drive 
which has been running continuously for 10 years.  The system which 
preceded it had a disk drive which ran continuously for 12 years.  I 
was glad to discard that disk drive (still working fine) since 
full-height disk drives are very loud and the capacity was small.

I have not heard mention of "stiction" 
(http://en.wikipedia.org/wiki/Stiction) for many years since a 
discussion with Ward Christensen (XMODEM inventor) on a forum in the 
early 90's.  As Ward described the issue, "stiction" is actually a 
problem with the heads sticking to the media and not a problem with 
the bearings.  The problem is completely gone now since all modern 
drives park their heads off of the media and don't leave them sitting 
on the media.  By the way, Ward recommends that if you encounter a 
drive with "stiction" and a solid hit on its side may free it up.

> (and as far as the Holographic drives go, I heard a detailed talk on 
> all of the error-correction mechanisms that had to be designed into 
> the InPhase drives.  While it may prove out to have solid 
> engineering, anything that needs as many layers and methods of error 
> correction as this drive does is a bit suspect from an archival 
> standpoint. With holographic storage, if you lose alignment of the

Tapes also use massive error-correction mechanisms. As bit density 
increases, the probability of error for a bit increases so either the 
error-correction encoding needs to increase, or else the user faces 
less reliability.

Regardless, the main question remains if the hardware to make sense of 
the medium still exists (and works) when it finally needs to be 
recovered.  These tape drives you like probably use specific 
interfaces which will require an archaic computer (with those failed 
hard drives) when it comes time to restore them.  The capacitors on 
those tape drives will have degraded and popped and joints will have 
corroded.  After even 20 years, it will be quite difficult to recover 
the content of a tape, or even find a computer which will interface 
with a hard drive.  This becomes more and more of a problem as 
technology continues to accellerate.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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