On Thu, Apr 01, 2010 at 08:23:41AM -0700, Wes Hardaker wrote:
> The last time I was at a store and was staring at the external USB
> hard-disks while holding a stack of re-writable DVDs I noticed that for
> about twice the stack of DVDs I could buy an external hard drive that
> I could always have connected and not worry about changing disks.  I
> haven't looked back since.

Of course, there are disadvantages too, especially if HDD is
connected all the time.

For example, the power surge that kills the main disks, might also
kill the HDD used for backups. An malign virus or software error or
user error ("rm -rf /" while mounted) might also nuke all your
backups as well as your main disk.

Also there is rendundancy in numbers - if you substitute one HDD for
100 of DVDs, you lose that redundancy (to gain convenience, of
course). But if your (one) backup HDD fails, you loose all your
backups. If one of your DVD dies however, there is quite a big chance
that you'll be able to recover some older state from some of the other
DVDs.

Thirdly (and that is specific to WORM media), no software activity
(like virus or user error) can erase backups from DVDs once they've
burned -- they are read only (and will only die with age)

You may alleviate some of the issues by buying stack od external HDDs
and rotating them on/off-site, but that will again lose you the
convenience (and gets more pricey). 


The main problem with DVDs however remains -- they are just too small
and too slow nowdays for anything but small sites...

So while there are solutions that are both convenient and relatively
secure, they tent to be pretty expensive. So there is no silver
bullet - the smaller sites just have to accept some disadvantages.
For some, DVDs might still be the best answer.

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