Date: Tue, 24 Feb 1998 19:49:42 -0600 (CST) From: Jay Nelson <jdn@acp.qiv.com> To: "Ben Kirkpatrick, ELI" <blkirk@float.eli.net> Cc: hackers@FreeBSD.ORG Subject: Re: SCSI Bus redundancy... Message-ID: <Pine.BSF.3.96.980224194109.1380A-100000@acp.qiv.com> In-Reply-To: <Pine.GSO.3.95.980224160907.26259E-100000@float.eli.net>
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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 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. 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 where you would see any benefit. -- Jay To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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