On Mon, Jan 16, 2023 at 9:48 PM Fred Cisin via cctalk <cctalk@classiccmp.org>
wrote:

> > What about M-DISC DVDs and BluRays?  Archival grade, not susceptible
> to magnetism or EMP.  I think BluRay discs are made of a harder material
> than DVDs and don’t scratch as easily.
>
> I have had magnetic, AND optical media that have "gone bad".
>
> I am interested in whatever media are more likely to still be readable in
> a few decades.
>

LTO tape, properly stored, is advertised as having a 30 year lifetime.  Of
course tape isn't particularly convenient for ad-hoc access so my archival
strategy is to dump things to a file server with a *lot* of disk space
(RAID1 or RAID10, not RAID0 or RAID4/RAID5), then regularly back up that
server to LTO tape.  The current generation (LTO8) is very expensive so I
use LTO4 and LTO6 tapes which are comparatively very affordable.  The data
doesn't tend to change but taking repeated backups anyway helps to ensure
that silent bit-rot on the hard disks is detected early enough to be
correctible.  Having backups on tape also has the advantage that the tapes
are easily moved off-site, so a fire or other such disaster won't take out
my server and my backups both at once.

There is another significant advantage to focusing on a backup strategy as
opposed to an archival strategy -- I don't need to worry about tapes I made
today being readable decades in the future (i.e. I don't need to worry
about keeping legacy tape drives running).  The file server is the
"archive" and I only *need* to be able to read the tapes I made last year
or last month.  If a tape drive fails I can just get another one, and if
they become hard to get there's nothing stopping me from upgrading to
something newer with better availability (i.e. I don't have a library of
old media that I need to be able to read forever).  The disadvantage of
course is that a file server isn't something you can reasonably put in
storage for future generations to access.  This strategy really only works
if the file server is accessed frequently so that
accessibility/compatibility issues can be fixed incrementally as they
happen (while they are still easily addressed using current/recent
technology).

-ken

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