Exabyte and file positioning...

[Paul Allen]

In article <8562 at brazos.Rice.edu> felix at warbucks.ai.sri.com (Felix Ingrand) writes:
>We are running 4.0.3 on a Sun-4/280.  Our Exabyte is on the SCSI port
>using the driver rst0. It looks like we are having some troubles with the
>file positioning on the tape. We are only using nrst0, and we are doing
>the following:
>
>tar xf /dev/nrst0
>mt -f /dev/nrst0 rew
>mt -f /dev/nrst0 fsf 1
>dump 4dsbf 54000 6000 100 /dev/nrst0 /dev/...
>
>And the dump failed...

I've been using Exabyte drives with Sun's 3.5 SCSI driver for a long time
with no trouble.  The piece of my backup system that actually copies the
data to tape has a 1Mb buffer and calls write(2) with a third argument of
1048576.  This worked fine until I upgraded one of my Exabyte servers to
4.0.3.  I got no indication of write failure, but could not read the
resulting tapes!  Through experimentation, I determined that using a write
size of 32768 or less would result in a good tape.  I would suggest trying
a dump block size of 64 or less.

Does anyone have any wisdom to share about 4.0.3 and Exabyte drives?  I've
heard it stated that you simply cannot use an Exabyte with 4.0.3 without a
patch tape.  While there may be a patch for some sort of a problem, I'm
certainly using one of my Exabyte drives under 4.0.3 without it.

I'm going to be upgrading a machine to 4.1, perhaps tomorrow.  One of the
experiments on my list is to attach an Exabyte and check it out.  I'll
have something to say in a week or so.

Paul L. Allen                       | pallen at atc.boeing.com
Boeing Advanced Technology Center   | ...!uw-beaver!bcsaic!pallen