Exabyte Hangs !!!

[Kemp at DOCKMASTER.NCSC.MIL]

Alan Broder <ajb at cornea.mitre.org> writes that extracting files using tar
from an Exabyte tape drive hangs part way through the tape, but that "tar
tv" will list the contents of the entire tape.  I suspect that it works
for listing but not for extracting because extracting (if it's to a local
SCSI disk) causes more SCSI bus activity.

We have been using Exabytes for about a month now, and I have also had
problems with permanent hangs.  The installation instructions for our
APUNIX software says to disable SCSI disconnects by editing the file
/sys/sundev/sc_conf.c:

 /* scsi disconnect/reconnect global enable flag */
 int scsi_disre_enable = 0;

The default value of 1 allows SCSI devices to disconnect and reconnect to
the SCSI bus.  According to the instructions, "You may be able to run with
disconnects enabled depending on what other devices you have attached to
the SCSI bus."

I first tried building the kernel with disconnects disabled, but when the
swap partition and everything else are on SCSI disks, the whole system
hangs while the tape is rewinding.  I then tried enabling disconnects, and
got the same symptoms as Alan:  the process using the Exabyte would hang
permanently, until a reboot.  We are now using the lesser of the two
evils:  temporary hangs with disconnects disabled.

This is on a Sun-4 running 4.0.1, which uses what Sun calls the sw
("SCSI-weird") driver.  How apropos.  Let's hope the new "Corporate SCSI"
driver works a little better than this.

   Dave Kemp <Kemp at dockmaster.ncsc.mil>

P.S.  Some Sun-spotter asked something like "How about that cute little
Sparcstation-1".  All I can say is BLETCH.  Frog Design laid an egg on
that one.  The dimpled front looks just like a big Band-Aid (tm).  I don't
want a computer that shouts LOOK AT ME - I'M A PIECE OF OFFICE ART!  If
only they had just shrunk the 3/60 cabinet down to 16"x16", now that would
have been a nice, quiet, classic design.