I am not anything more than an amateur historian, but my career has been
in Information Technology so I have something to offer back to this
great list.
CD's and DVD's are great for portable, short term storage. As has been
discussed on this list, they are not true archival formats and should
not be relied on as such. At the best, you'll get read errors as certain
sectors break down which might render a few files unreadable. At the
worst, the entire disc will be unreadable. Interestingly enough, even
music CD's are prone to this problem - I have a few music discs that I
purchased back in the early 1990s that are showing signs of CD rot.
Magnetic tapes are generally the accepted way of archiving data for long
term use. A properly cared for tape will last somewhere between 30 to
(they claim, obviously this has not been tested yet) 100 years. Tapes
created in the 1970s are still readable today, provided that the actual
hardware needed to read these tapes is still available and serviceable.
Tape also has the advantage of being able to hold far, far more than
even dual layer DVD's can. The native (uncompressed) format of LTO3
tape, for example, can hold 400GB of data, and with compression hold
double that. It's also more cost effective, being about $70 on the
street, although the drive itself will cost far far more.
With the declining prices of hard drives these days, I am tempted to
suggest getting several external hard disks and using them to archive
files. I would make exact copies of the data on each disk, and keep them
in a climate controlled environment. The most important consideration
for the storage of magnetic media (hard disk/tape) is to keep the
devices away from any electromagnetic fields.
You can also use a piece of software to create what is known as parity
archives. Say you had a bunch of pictures that you wanted to store for
long term use. You could archive them into chunks using WinRAR (RAR is
open enough of a format that I would expect it to be readable far enough
in the future) then use a program like QuickPAR to create parity
archives. If some of those RAR archives get corrupted or damaged, you
can use the PAR archives to restore them. It's a pretty ingenious system.
http://www.par2.net
Of course you would always want to do test reads/restores every so often
to ensure the quality of the archive and to move the data to new formats
if it looks like the old one is in danger of dying out.
I hope this was at least somewhat enlightening.
Yours,
Ben Ruset
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