Re: mirrored machines via network

Ian Main (
Mon, 4 Nov 1996 12:03:04 -0800 (PST)

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.
>> 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

I'm not the most knowledgable person that's for sure, but I'll tell you
what I think anyway ;) I think the idea below is a better one. Having
the machines swap IP's when the master goes down.

Couldn't this be done with a shell script?

ie. (massively simplified version)

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?

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

Just my .02c worth of thoughts ;)

>how about clients who use nonauthoritative answers from caching servers
>elsewhere on the net?

yup.. this would be a big prob AFAIK. [what about TTL (time to live)
setting? or was that called something else? I know there's a setting in
the DNS to control how long caching servers should keep the record.]

>> Last but not least, if anyone has seen this or anything similar, please let me
>> know. I looked long and hard for something similar, but I'm sure my search
>there is a product called openvision (i believe now called axxion
>something) that does this. i don't recall the vendor offhand. they have
>two machines connected via a private network, and share a pair of IP
>addresses on their public network interfaces. the active pings the
>standby witha UDP heartbeat. if the standby stops getting heartbeats, it
>reboots the active, swaps IP addresses, and becomes the active. dunno how
>they tell everyone else the change in physical to IP address mapping.
>apparently it works for ethernet but not fddi public interfaces.
>you can get some funky software to work with this called disksuite. it
>shares a scsi bus between the two machines so you get the exact disk
>state at the time the active died. dunno how they do that.
> Ray Lehtiniemi <>