Re: tapes best for backup?
On Sat, Jan 05, 2008 at 12:46:11AM -0600, David Dyer-Bennet wrote:
> Why do you think DLTs are more reliable than optical media or hard
> drives? My experience with tapes in general (not DLTs) certainly does
> not predispose me towards that view, but I suppose DLTs could be
> "different".
> I've never had a CD or DVD go bad once it passed verification, and some
> of my cds are from the early 1990s (Kodak Photo CDs). I *have* had
> tapes in every format I've ever used, from 7-track up to DDS, go bad or
> be unreadable for other reasons. I've also had a lot of the *drives* go
> bad, which means I'd probably want two or three before storing anything
> important on the tape format.
>
I started this thread on debian-user after a thread on OpenBSD berated
someone for relying on CD/DVDs for backups and archives because they
fade over time. Their attitude is that tape is still the only viable
medium for long-term storage. They also said that hard drives kept
off-line get "bit rot" while if left on-line they are at risk of the
same power surge and most other threats to which is the main data.
I observed that, based on what I see on e.g ibm's website that the trend
in enterprise stuff is toward virtual tape libraries that are really a
bunch of hard disks that appear to the network and its apps as if it
were a tape library. The answer was that those are purchased by crazy
managers.
So I've been specifically asking about archives. Sure, if you keep
backing-up the same data, you continually get feedback if the media is
getting flaky. The answer on DU seems to be that while some sites use
tape, others just keep everything on line and for off-site backup, the
data goes somewhere else where it is also kept on-line. I.e. why bother
archiving?
DLT and LTO are supposed to be guaranteed for 30 years. DDS for about
10 years. We haven't had DVDs that long. We haven't had USB sticks
that long. Hard drives that right now are 10 years old are considered
unreliable. Then again, tape drives don't last that long and the
practice seems to be that if you really need to archive data for 30
years, to store a new-but-tested drive or two with the backup tapes.
The only personal experience I have had with computer tapes is my
Irwin/IBM QIC-80 100 MB that I bought with my first computer (IBM PS/2
386). I have had those tapes fail but only noticed when writing. The
only time I needed that backup was when the 386's motherboard warped
like a cookie sheet in the oven (room temp 35 C, we had no A/C). I
bought my IBM 486, put the tape drive in it (after convincing IBM to
give me an adapter to allow me to connect the drive) and did a restore.
When I moved from OS/2 to Linux, the QIC isn't supported so I switched
to ZIP disks and they have always worked.
Interestingly enough, I can still use the IBM floppies that an old
version of OS/2 came on in 1988. I've had new floppies fail but not
those old IBM ones. Go figure.
So I guess, for me, only from personal experience, I'd have to say that
the most reliable, longest lived, backup media has to be IBM floppies.
Of course, the 7 GB backup would take 5120 floppies which would more
than pay for a new LTO drive.
Progress.
Doug.
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