[conspire] DVD as backup media

[Rick Moen]

Just posting some comments I made to a friend in private mail.

> I am sure that your next machine will have a dvd burner. When you
> consider that a dvd holds over 6 times as much as a cd, it makes
> a great backup and think of how many fewer disks it would take
> to hold all those different cd's full of distros you have.
 
I suspect DVDs make good archival media but really dreadful backup
media, for pretty much exactly the reasons that CDR[W] have been a dumb 
choice before them:  Prices for DVD-R media seem variable and subject to
gimmicky conditions, but generally run about $1 per disk in bulk, give
or take.  Full-size DVD-RW media seem to run about $3 per disk in bulk.
Experience with CDRW suggests that erasure is slow and doesn't work
properly very many times in a row.

DDS3 tape media are cheaper per gigabyte at acquisition and have vastly
greater service life.  Also, backup software is capable of cataloguing
contents of backup sets on those tapes such that you can restore
specific files as of specific dates, at will -- but not for DVD-R[W].

People are forever suggesting completely unsuitable and/or uneconomical 
media for backup.  This used to surprise me, but doesn't any more.  The
common thread seems to be that the person making the suggestion owns
hardware that makes that kind of backup physically possible, and isn't
really familiar enough with real backup economics and logistics to see
why it's a non-starter.