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Date:      Thu, 13 Jan 2000 04:32:05 +0800
From:      Peter Wemm <peter@netplex.com.au>
To:        "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
Cc:        mb@imp.ch (Martin Blapp), current@FreeBSD.ORG
Subject:   Re: move portmap(8) from /usr/sbin to /sbin 
Message-ID:  <20000112203205.B58A01CD7@overcee.netplex.com.au>
In-Reply-To: Message from "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>  of "Wed, 12 Jan 2000 09:27:00 PST." <200001121727.JAA28834@gndrsh.dnsmgr.net> 

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"Rodney W. Grimes" wrote:
> > "Rodney W. Grimes" wrote:
> > [..]
> > > So no disk, so just what is it that you are exporting???
> > 
> > Just a comment:
> > 
> > I've seen scenarios where a local disk is attached holding a kernel,
> > bootblocks loader etc, but otherwise booting from a server over NFS.  And
> > it exported the rest of it's disk for general use...  It's easier than
> > netbooting, allows each machine to contribute disk space to the cluster in
> > addition to compute cycles, keyboard, screen etc.
> 
> See other mail about the evilness of cross mounting NFS, this especially
> applies in a cluster!  You can't bloody cold start the beast easily.

Yes you can..  I didn't say the boxes depended on each other to boot.
They had a NFS server for the OS for /, /usr etc.  They cross mounted the
exported space between the boxes via 'amd' which happens much later (and is
in /usr).  The seperate server depended on nothing.

> One way I have seen it worked around is to flag the NFS mounts -background
> so that they don't hang the boot process.  Still evil lurks in these
> corners of the world...

Or don't mount it early in the boot.  I'm not suggesting moving portmap
BTW, I'm just saying that there are other ways of doing it.  Yes, having
cross mounting required to *boot* is evil, but when it's not active until
somebody logs in it's mostly harmless.

On an unrelated note, I remember the cold-start nightmare scenario well. One
of the local universities had a cluster of SGI IRIS boxes, way back when they
were new and had tiny disks.  There was a power out and the cross mounting in
order to preserve every scrap of space caused quite a lot of excitement.

Cheers,
-Peter




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