Disaster in progress: disk is dying, tape doesn't work :-(

[Doug Ledford]

Randy Gobbel wrote:
> I just blew my entire weekend in a futile attempt to back up my system before
> it becomes unuseable.  I tried running dump with every possible combination of
> block size setting, and sync/async, enable/disable disconnect, using both a
> 2.0.35 and a 2.1.122 kernel.  It would be nice if the aic7xxx driver has some
> options for more verbosity--even with verbose==0xffff it never said that the
> tape drive was *not* synchronous, or that disconnect was disabled.

You can always find out by typing "more /proc/scsi/aic7xxx/0" and it will
tell you.  The Disconnection enabled flags entry is a bit mask that should
normally be 0xffff and the speed your device is using to communicate will be
list with the device (assuming you use the latest aic7xxx driver).

> In 2.0.35, dumps would almost always complete without any error messages, but
> I was unable to get "restore -C" (i.e., verify) to get very far before
> complaining about massive numbers of errors.

99% of the time if I have problems with a tape backup of any kind, it's a
bad tape.

>  I'm not sure whether the tape is
> really unreadable, or the software is broken.  In 2.1.122, things are much
> worse: dump gets all the way to the end, then hangs trying to close the tape.

This, I believe, is a bug in the 2.1.122 tape driver.

> All dumps were run in single-user mode.  The tape drive is a Conner (i.e.,
> Seagate) CTT8000-S Travan TR4 drive, firmware 1.22.  The disk is a Quantum
> Atlas I, firmware L915, and the adapter is a 2940UW with firmware 1.23.  I'm
> running driver 5.1.0pre12.
> 
> I could really use some hints about what SCSI parameters are most likely to be
> right for a tape drive, re: disconnect and sync/async.  It appears that
> disabling disconnect doesn't really work at all, because it causes the disk to
> get tons of SCSI timeouts.  Async/sync I'm not sure about--I really don't
> understand the pros and cons of each mode.

Enable disconnection and sync negotiation.  Things will go much smoother
that way.  The disable disconnection is working perfectly if you get tons of
timeout errors since what that does is make it so that when the tape drive
is busy, other devices like the disk drive aren't allowed to use the SCSI
bus.

> If anyone out there has *ANY* suggestions about what to do here, I would
> really appreciate hearing from you.  I'm getting desperate at this point, and
> the number of grown defects is outrageous and growing rapidly: 963 when I
> looked just now.  If this is not an emergency I don't know what would be....

Get a new tape, clean the tape drive, do a complete dump, then put the tape
away and pray that it does the trick when you have a drive to replace your
failing one.

-- 

 Doug Ledford  <dledford at dialnet.net>
  Opinions expressed are my own, but
     they should be everybody's.

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