Re: Redundancy

Armistead, Jason wrote:
>
> Now, if you want REAL redundancy, then maybe an OpenVMS port of Squid
> would be useful. The supplied TCP/IP stack on new AlphaServers is
> Digital's UCX, which can support "cluster aliasing" of IP addresses.
> i.e. many machines share one IP address. There are two modes, the first
> is round-robin, kind of like DNS, but it's decided on purely by the
> machines, so the clients remain blissfully unaware, and the second is a
> load-balanced implementation, where the computed load metric determines
> which machine is assigned the control of the cluster IP address.
>
> If Squid could be ported to OpenVMS (hey, it does use pretty standard C
> constructs, doesn't it), then it might be doable. Just make each
> machine point to the other as a sibling, so that hit rate is maximised,
> even with two different cache directories. Then give users the cluster
> IP alias to point to.

Doesn't help with anything other than a system outage (intentional or
othewise), as I understand it. The cluster alias IP address goes to
whichever system is picked by the software at the VMS end (only one system
at any particular time, can't transfer to a different system while any
connections exist), and all connections to the cluster alias address go
there. Or that's my understanding of it (having worked on VMS for many years
before switching mainly to UNIX, though the IP cluster alias facility is not
something I've actually used).

The situations that I, and some of the other comments, raised are when Squid
itself either rejects connections or ignores them for an extended period
during "housekeeping" activities; I don't see how the VMS cluster alias
could help with that - connections would still be routed to the same working
system and the same unresponsive Squid.

                                John line

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