On Tue, 31 Jan 2023, Steve Lewis via cctalk wrote:
...
What do you guys think of the "archive-ness" of current solid state
devices? M.2, NVMe, SSD, or even USB thumb sticks? A friend proposed
that when one of those starts to go bad, any kind of partial data recovery
becomes difficult - but any more difficult than the old traditional
magnetic media?
some thoughts, albeit no technical insights:
Still a problem.
With spinning rust, you can bypass some of the mechanisms involved in
normal reading, in order to get at a more "raw" version of what is
recorded. Such as GreaseWeazle. Thus, a corrupted sector header,
or a parity error, that migh lock you out of access using "normal" means
can be examined. In the case of only a few bits being bad, it can be
manually repaired, albeit with considerable manual labor.
I know the first generation CD/DVD disc are known to "go bad" - the
material itself somehow degrades and becomes unreadable by modern drives.
I'm not sure if that's still the case with newer or more modern CD/DVD disc
(not just that they're newer, but are they a more durable material or
casing?)
Current media is better than the early stuff.
But, it is still susceptible to degradation and/or damage.
All of my DVDs are also imaged on spinning rust. (I have been told that
it is legal to do so with commercial DVDs using ANYDVD, although
marketing, or even creating, such a tool runs afoul of certain laws)
The latest variety of optical media, "MDISC", claims extreme longevity,
while maintining full compatability with being read by "legacy" systems.
But, obviously real testing of such claims (rather than simulations or
extrapolations from stress testing) will take time.
It does look like a good step away forward in protection against
degradation.
Although, the higher the density (MDISC BDXL is available at 100GB on a
disc), the less amenable it is to out of channel access for repair.
Obviously, distributed redundancy of storage is the only practical way to
protect against damage. But, that is of susbstantially less effectiveness
against degradation. In the relatively early stages of degradation, it
can help to recognize when degradation is occuring, simply by seeing a
copy go bad as a signal to check the other copies.
Multiple forms of the media, such as copying to every new form of media
periodically serves to increase redundancy, and having mutilple media
types reduces the possibilities of multiple copies degrading.
Occasionally, the tools and knowledge to access some media are lost.
News reports let us know that the sky is falling.
There is a fair amount of "reinventing the wheel" done to recover content
that might still be trivial for othere.
Multiple forms of media is the obvious way.
The Egyptioan hieroglyphics were unreadable for a while, until somebody
lucked onto a multi-form document (Rosetta Stone).
Much of what is known about StoneHenge is purely speculation. (although I
have a trivially simple hypothesis about HOW "they managed incredible
calculations" for the placement of the stones.)
--
Grumpy Ol' Fred ci...@xenosoft.com
