Dan Wright wrote:
Jerome Fine said:
I don't know about retention, but I expect I
will be making a backup of the
long term files about every one or two years. Does anyone know how I
might test a magneto optical cartridge for long term degradation? Also,
if I can read the cartridge, does that indicate it is as good as when it
was written or should it always be written again after 5 years just to be
sure?
Well, I don't know for sure, but I expect they're pretty good. I
know of a
local company that has ~1TB of records dating back many years on MO media, and
they use them regularly (as I understand it, anyway; I don't actually work
there) so the data's probably pretty stable...
Jerome Fine replies:
I guess the key question is:
"How does a user evaluate the longevity of any particular media?"
It seems unlikely that the microwave is a good fit for testing magneto optical
media. On the other hand, I would like to have some sort of idea as to how
long I can expect any files to still be readable? Also, how long is it likely
that the magneto optical drive will last. I suspect that the drives are likely
to fail before the media and it may even be more likely that I will not be able
to find a system that is able to use both the old drives and the newest drives
when it comes time to switching to a newer type. So the next question is:
"What sort of strategy is recommended to always be sure that old files (stored
on old media which can only be read with old drives) be rescued/copied to newer
media before that is no longer possible?"
Obviously, every user would like to skip as many in-between steps as possible.
But since safety is perhaps more important, where should the compromise be made?
Another question is:
"What standard needs to be used to determine what files may be of interest in
50 years, 500 years or even 5000 years?"
And realize that is probably THREE SEPARATE questions!!
It is fine to be discussing the technical details of how to save files, but if everything
needs to be saved, that creates many difficulties. For example, if some software
is being developed, it's rare that non-distribution files ever see the light of day,
much
less that they get saved beyond the next distribution. In most cases, only the final
source and executable files get saved and it is probably rare for OBJ and MAP files
to be saved. What is the best way to develop criteria that can determine which
files will be of interest to someone looking to understand how "programs" were
written 5000 years ago? Better still would be to attempt to determine the questions
that will be asked 5000 years from now. Looking back, I would suggest that the
first footstep on the Moon back in 1969 may not have been as important as the
technology that was needed to make it all possible.
I realize that this seems Off Topic, but I think it is already past due that we think
about not only which hardware needs to be preserved, but also all the software.
So much that is more than 20 years old has already been lost. But if a start is
made right now to preserve both hardware and software, then for software the
questions are very different than for hardware!
Sincerely yours,
Jerome Fine