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From: kai@sp1.csrd.uiuc.edu (Kuck And Associates)
Newsgroups: comp.sys.sequent
Subject: info about 8mm drive on Sequent
Message-ID: <1990Jul25.160107.4360@csrd.uiuc.edu>
Date: 25 Jul 90 16:01:07 GMT
Sender: usenet@csrd.uiuc.edu (news)
Distribution: comp
Organization: UIUC Center for Supercomputing Research and Development
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I just moved our 8mm cartridge tape drive (a Megatape GT88/1) from our Alliant
FX/8 to our Sequent Balance B8.  On the Alliant, it was daisy chained along
with a Telex 9250 to a single Xylogics 472 multibus Pertec tape drive
controller.  I learned that Sequent only supports a maximum of two tape drives
on a 472, and they must be the same device type, sharing one tape drive
formatter.  We can't daisy chain the two dis-similar drives the way Alliant
does, with the first drive connected as device 0 (formatter 0), and second
drive as device 4 (formatter 1).

With some help from tech support, I found that it is possible to put a second
Xylogics 472 (we do have two) in our B8's lone multibus chassis, but then we
can only use one tape drive at a time.  To use both tape drives at the same
time would require installing a second multibus chassis, and installing the
second tape drive controller there.

I have not seen this limitation mentioned in the discussion about Sequent's 8mm
drive.  It does explain why Sequent sells their drive with a separate controller.

If Sequent's "zt" driver supported all eight drives that the 472 supports, this
problem would be eliminated, and the 8mm drive would be cheaper to install.

I'll report next week how monthly full backups go this coming weekend.  I'll be
using the plain old "dump" command that came with our Balance to write to the
8mm drive, now that it's a local device, and we'll find out if Sequent's
"hdump" program really is neccessary.

	Patrick Wolfe   (pat@kai.com, kailand!pat)
	System Programmer/Operations Manager, Kuck & Associates
	"Any opinions expressed are my own, not my employers's.
	 Please don't call my boss and complain ... again."