Re: mirrored machines via network

Peter Rival (
Sat, 2 Nov 1996 17:33:18 -0500 (EST)


On Mon, 4 Nov 1996, Ian Main wrote:
> On Fri, 1 Nov 1996, Ray Lehtiniemi wrote:
> >On Fri, 1 Nov 1996, James R. Leu wrote:
> >> operations of a small ISP. I am looking into ways of implementing redundant
> >> servers.
> >[snip]
> >> The idea I have, necessitates two main developments. The first of which is
> >> a "intelligent" name-server. I have begun development of this already. I have
> >> started by using th bind-4.x.x source. The end result will hopefully be a
> >> name-server that checks if a machine is responding, before it gives out the IP
<snip simplification reasoning>
> ping master
> if no response ifconfig eth0 down
> ifconfig eth0 <master_ip> up
> so long as they're on the same subnet, it should work no?

Yes, it (could) work. However, I see two potential probs with that
idea. One - how do you decide how often (and how much) to ping the master?
Granted ICMP echo requests aren't all that large for packets, but in this day
and age, we need all the spare bandwith we can get. And two - what happens if
you lose the entire segment? (I know, scream bloody murder and turn on the
coffee pot...;) If you could set up the master DNS server to check on the
state of the server (I think the newest version of lbnamed does this) before
returning the IP, you could put them on separate segments and hopefully have
a little more redundancy.

> Now all you have to deal with is dropped connections, and the mirroring of
> the HD.

Well, that's where this idea kinda falls apart. Unless you can write
some really schnazzy clustering software that works _reliably_ through a
router. I know there are things out there like this...unfortunately, I've
gotta go install an AIX (eeww...hate that word) box, so I don't have the time
to try to research it. Quick thought - Auspex does do something like this,
but I don't think it solves the separate segment thing.

- Pete

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