Re: Wait for dumping
2005-09-18 12:37:16
Jon LaBadie wrote:
On Sat, Sep 17, 2005 at 11:25:48PM -0400, Florian Lengyel wrote:
Here's the post-mortem: I've been using a hand-me-dowm
Spectra Logic 2K. No matter what tape I tried in drive 0
(the only one of two that my AMANDA configuration seems
to recognize) I had I/O errors. Even an innocuous command such as
mt -f /dev/nst0 compression off
[by the way, the argument "off" is worth a small fortune in
consulting fees, since it has to be guessed]
Resulted in an I/O error. Such things are often caused by
hardware trouble. After checking cables, interface card seating,
and other things, I tried using the cleaning tape.
Problem solved.
You wouldn't think a 'compression off' request would have
any involvement with possibly dirty heads.
Well, the advice is to let AMANDA do its compression; without
compression the drive is presumably going to be doing more work.
I wasn't mentioning compression in that connection; I meant to suggest
by example that no matter what I did, I was getting I/O errors.
Also, in the UNIX documentation I've seen, the mt compression operation
is described, but the "off" flag is not. I've searched in vain for
this--made a career of it, in fact. I believe there was one obscure web
page on this, in Latvian.
Here is a guess,
I've seen some tape drives that when an error happens flag
the error and refuse to do anything until it is cleared.
At one client they had a DLT drive. Anything went wrong
and the "clean drive" light came on. Then you could do
nothing unless you cleaned it or 'I think' there was some
manual way to turn off the light. Maybe power off/on :)
The Spectra Logic 2K's changer LED did turn a jaundiced, tape-weary
amber. Power cycling the drive did nothing. Only the wildly inspired
guess of inserting the cleaning tape helped. RTFM time, especially
since the spectral logicians at Spectra Logic won't discuss my 2K
without a service agreement.
BTW you mention you have other ?drives? not being seen?
Based on replies here, most linux kernels default to only
scanning LUN 0 on the scsi buss. Some configuation change
lets it scan others. Similarly on my Solaris system, by
default only scsi IDs 0-7 are scanned for tape drives.
Again a config setting allows IDs 8-15 to be scanned.
Maybe something similar is your problem.
I have a lot of problems; on the subject of tape backup, the Spectra
Logic has two internal drives. The mtx command sees both (and numbers
them 0 and 1), and the kernel appears to see both. However, Gene
Heskett, in an email after this one, mentions that Red Hat doesn't
bother to scan for both SCSI drives. I may have told a fib: I'm using
CentOS on my AMANDA server. Perhaps I should punish CentOS and install
Debian instead.
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