Backup recommendations

[James Wilkinson]

Stuart wrote:
> So I am thinking about writing critical stuff to dvd 
> periodically but I have read conflicting comments about
> the longevity of writable dvd's.
> Any comments?

Quite how much do you want to back up?

In my case, it still fits nicely onto a DVD -- in fact, my data
collection seems to be growing at a similar rate to consumer writeable
media. So in my case, I simply take a backup off-site periodically.

If my house burns down, my last off-site backup should only be a few
weeks old, not ten years.

Having said that, I would *also* recommend that you keep checksums of the
files somewhere, and to check them periodically (you should be able to
script this, if you're that way inclined). Unless you've got the
(somewhat more expensive) ECC memory, it's *possible* for files to be
silently corrupted when they're copied, due to the very occasional errors
you get with non-ECC memory.

Using checksums will help you catch this.

One other thing you will want to bear in mind is the readability of file
formats. Professional archivists worry a lot about this -- data gets
archived, and then decades later, it turns out that you can't get the
machines to physically read the data (for example, they were written on
5.25 inch floppy disks, or paper tape). Even if you can read the data,
you have to write custom software to decode it, and you *hope* that the
data format is sufficiently well documented.

No-one's quite sure how this is going to play out in the consumer digital
world yet. Twenty years ago, one might have been saving image files as
Amiga IFF or MacPaint files -- support for them is still in the current
generation of "do-everything" graphics editors. One might expect and hope
that JPEG and (by-then patent-free) MP3 support will still be available
in the successor programs in twenty years time. But at that point, it
might be time to transcode them into newer formats.

At that point, still having the data loss of MP3 format or JPEG in your
data might be annoying, since there's no longer any technical reason for
the data loss.

Hope this helps,

James.

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