archiving data, was RE: Media Longitevity/Care

Tom Jennings tomj at wps.com
Thu Mar 17 02:32:57 CST 2005


On Wed, 16 Mar 2005, Dwight K. Elvey wrote:

> This does require regular reading of the archived disk. This
> is not necessarily an easy thing to do.

I'd like to offer that there is no such thing as archival computer
media. None.

Dwight's comment is succinct; all offline storage needs to be
checked. Literally all of it is rotting on the shelf.

(For short-term backup, eg. data loss prevention, this logic
doesn't apply so directly.)

It's a lot of work to check archival data; nearly no one does it
right, and it mostly amounts to spot checks (a valid method
certainly but in itself an admission of the scope of the problem).

I don't do "backups" per se; I keep everything on rotating
spindles, aka hard disks in running systems. If you pause to
consider what this means as a long-term solution, it sounds really
precarious, because it is; but in fact it's *less precarious* than
any form of offline storage because it is essentially 100%
continuously monitored, embedded in a live computer.

I have five computers in four physically distinct locations (three
are >> 100 miles apart) with enough storage to hold literally all
the computer-readable data I own.

If you somehow think that tapes stored in a controlled vault is
more reliable, or less susceptible to bit rot than rotating
spindles, I believe you are wrong (and my every experience and
observation says otherwise). Only fiche and paper are statically
reliable.

It's no crazier to think that my data (sic) will reside on a
series of continuously operating computers for the next N decades
than it is that a CD-R or DVD-R will last as long, or be readable
N decades in the future.

Yes, in one sense it makes me nervous. That's good! Dump tapes
sitting in a closet or bank vault are rotting and becoming
spectacularly incompatible; it just doesn't generally make people
nervouse, but it should.

Hard disk storage also neatly avoids the incompatible-media issue;
it's continuously ported, incrementally. The translation issues
are from M to M+1, far less than trying to deal with 8" floppies,
1/2" tape or other once-standard media.

Also, for the moment at least, disks of tomorrow are chealer and
larger than disks of today, neatly taking care of increasing data
size (for how long this will hold out I don't know).

Whether you have 10MB or 1 TB of data, it's still cheaper with
rotating spindles. If you've really got a terabyte of data to
reliably save, backup tape isn't cheaper -- if you include the
longevity issue, of translating last-years tapes to next-years
tape. Who does that? Not many...

It's not about the medium, it's about the data. All of our mediums
suck for archival purposes, except paper and fiche.
Generally-speaking, our cultures don't directly care about
preserving the future, and machine media is a narrower case of
that.



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