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From: alan@shodha.enet.dec.com ( Alan's Home for Wayward Notes File.)
Newsgroups: comp.sys.dec
Subject: Re: can ultrix and vms share an HSC?
Summary: Maybe, but it's not supported.
Message-ID: <2801@shodha.enet.dec.com>
Date: 23 Mar 91 01:34:17 GMT
References: <1991Mar22.154344.21227@uservx.afwl.af.mil>
Organization: Digital Equipment Corp. - Colorado Springs, CO.
Lines: 42

In article <1991Mar22.154344.21227@uservx.afwl.af.mil>, ridout@uservx.afwl.af.mil writes:
> So my question is: Can I have my VMS vax and Ultrix VAX connected to the same
> star and use the same HSC to share the tape drives?

	Probably, but it's not a supported configuration.  Most examples
	I've heard of work without much trouble.  Sharing just the tape
	drives is probably the safest way to go.

> And to extend the question a bit further, can the disks remain on the 
> HSC  i.e. some of the disks on the HSC belong to the VMS machine and 
> some of the disks belong to the Ultrix machine.

	You could do it this way.  But, have you heard of the evils
	of a partitioned cluster.  One where multiple uncooperating
	system are accessing the same disk and slowly trashing the
	contents.  An ULTRIX and VMS sharing the same HSC is a fine
	example of one of these about to happen.  All it takes is
	an operator accidently doing an INIT/ERASE on the ULTRIX user
	disk, or on the ULTRIX system someone doing an newfs(8) on 
	the VMS system disk.

	There are tricks you can do to reduce the chance of something
	like happening.  On the ULTRIX side you just take the VMS
	disks out of the configuration file.  From the VMS you might
	be set the device NOAVAILABLE (or whatever it is).  If you
	only one system accessing a disk you can set it exclusive
	access for that host from the HSC.  You'll have to redo this
	part if the HSC reboots.

	If you can put the disks that the ULTRIX system on local
	disk controllers this is best.  Then as money permits get
	a 2nd Star Coupler and HSC for the ULTRIX system.  Another
	possibility if you have a VAX 6000 (or VAX 9000) as the
	ULTRIX system is to get a CIXCD and connect the tapes to
	it.  If the tape are dual ported you'll have to give this
	up, though.
> -- 
> *  Brian Ridout                  What's the difference between a CAR       *


-- 
Alan Rollow				alan@nabeth.cxn.dec.com