On Wed, 2010-03-24 at 15:09 -0500, Marcio Vogel Merlone dos Santos
wrote:
> What is the best strategy and storage media for long-term backups,
> say
> to 10 or 20 years (if any)? I ask because I do have an old DLT tape
> drive and some tapes, unusable, because its SCSI controller is no
> longer
> among us. It is not 10 years old and is already a problem.
There's really not a single best answer to this, in my opinion.
Long-term archiving is a complex, multi-faceted problem, and solving
this problem is an IT discipline unto itself and not my personal
specialty.
What *I* prefer to do -- though YMMV, and archival specialists probably
think I'm nuts -- is to keep my backups on live media such as hard
drives rather than traditional removable media. But I maintain and
upgrade that live media with each technology generation. In other words,
I don't try to make a single medium last for more than 3-5 years. This
works well for my situation of a couple terabytes, with today's drives,
but it doesn't scale to a large enterprise where data is counted in
exabytes. We back up to an "octopus" of 1 TB USB drives and rotate
drives off-site. We're about to implement redundant octopi so that we
have at least two copies of everything, and we these will be at two
different data centers. iSCSI offers some interesting options for
building this kind of solution.
You can also use offline media but be selective about what standards you
choose. Tapes that are peculiar to one manufacturer and model of drive
are a bad long-term choice, but something that is a multi-sourced
industry standard is likely to be readable further into the future. Take
floppy disks, for example -- way past obsolete, and hardly anyone has an
old-fashioned Intel 8272 style FDD controller. But you can still buy USB
3.5" floppy drives even though USB wasn't even invented when floppies
were current technology.
I would predict that CDROM and DVDROM media will be similarly long-lived
in that you will be able to buy readers for them far into the future.
These also have the advantage of their format being ISO 9660 standard.
But their capacity is very limited. The jury is still out on Blu-Ray
media's long-term archival stability.
The other thing to consider with archiving is the internal file format
of your data. Try to read a document from Microsoft Word 2.0 today and
see how much of it is comprehensible to modern versions. I recommend
spinning out proprietary formats into PDF or RTF or plain text versions
-- again, something that is a published standard -- alongside the
vendor-specific format, so that in the future even if you can't read the
original you are still likely to be able to retrieve the basics from the
less-rich but more standardized open format. Programs like
"antiword" (which is Open Source) can automate some of the export
process, albeit with some loss of formatting. That's why you keep both
the original and the exported copy -- the copy is your "last resort" if
you can't read the rich-format original.
In other words, you could have the best archival *media* in the world
but still be unable to recover data if you can't read the file format
any more. I've seen this aspect ignored a lot.
Scott
--
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Scott D. COURTNEY, Principal Engineer Sine Nomine Associates
scourtney AT sinenomine DOT net http://www.sinenomine.net/
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