Date: Wed, 25 Feb 1998 19:48:31 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: jdn@acp.qiv.com (Jay Nelson) Cc: blkirk@float.eli.net, hackers@FreeBSD.ORG Subject: Re: SCSI Bus redundancy... Message-ID: <199802251848.TAA01481@yedi.iaf.nl> In-Reply-To: <Pine.BSF.3.96.980224194109.1380A-100000@acp.qiv.com> from Jay Nelson at "Feb 24, 98 07:49:42 pm"
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As Jay Nelson wrote... > On Tue, 24 Feb 1998, Ben Kirkpatrick, ELI wrote: > > > I've been wondering about the scsi redundancy problems that come up now > >and then (read: I've been chewing on paint chips again). What parts are > >failing? In my experience, only disks have failed once installed; > >controllers have only failed during poor installations and very rare at > >that. > > But what I was really wondering, is this about have two SCSI cards on > >one scsi bus. On one of my old adaptec's it _looks_ like I can change the > >controller from ID7 to anything else. With a controller at say 6 and 7, > >would there be a way in software for both controllers to access the disks? > >Or even for the standby controller to just scan the bus now and then? > > Okey, I'm going off the deep-end, back to my white-out (old-formula). > > > >--Ben Kirkpatrick > This is normally done with differential controllers between two > different machines -- and, yes, it works. I don't think it's possible See Digital Unix TruClusters, they indeed only want differential for the shared SCSI buses. > with single ended controllers. Concurrent file access from two > different machines is a _lot_ more troublesome because of the locking > problems. I don't know of any standard Unices that support this out of > the box. It usually takes two special daemons that run on both > machines willing to communicate with each other. Digital Unix TruClusters do DRD (distributed raw device) now. Things like Oracle Parallel Server love this. A cluster filesystem is another kettle of fish of course. But not impossible, see OpenVMS. > If you want both controllers on the same machine for high > availability, you'll need to write some software to monitor status and > take the appropriate actions if there is a failure. Otherwise, I don't See www.veritas.com for a number of whitepapers on High Availabilty. Veritas calls their product FirstWatch. Wilko _ ______________________________________________________________________ | / o / / _ Bulte email: wilko @ yedi.iaf.nl http://www.tcja.nl/~wilko |/|/ / / /( (_) Arnhem, The Netherlands - Do, or do not. There is no 'try' --------------- Support your local daemons: run [Free,Net,Open]BSD Unix -- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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