Exchange 2003 SP 1 Cluster - Good Failover solution?

I am researching a cluster environment for proper disaster recovery for Exchange -- the main purpose is high availability...the only experience I have with this type of failover is using Legato CoStandby server, etc.  Would clustering work for the following need:

* One Exchange Svr on location, one offsite
* If the Active node in the cluster on location goes down, one offsite takes over

I saw that they both need a "private LAN" connection to communicate with each other -- would this work over a PTP connection to a remote site?  Also, if the shared storage location for the information store is a NAS storage device, doesn't that make for a single point of failure?  Would it be better to have the NAS device at the location and a backup NAS at the offsite location?
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The intension of a cluster is to have a "on the fly" take over, what means, that the cluster has to keep the servers in sync all the time, what take some bandwidth. This is one of the reasons, why cluster servers are using a dedicated network to each other. Usually, a gigabit connection is used by most of the current servers. Needless to say, that connecting a cluster over a remote connection is not really, what you can call recommended and a remote line is also always a point of failure.

A single NAS device within a cluster is a second failover bottleneck, as long as the NAS is working, the failover is no problem, but if the NAS device has a problem, your fine cluster is something for the trash. If you want to have a really "high availability" configuration, you will also need a failover NAS of course.

The only reason I would accept to "share" a cluster on two different locations would be, to have something like a fire protection, but connected with a cable together. Whenever you have a local problem, the second location can take over the work (as long as you can work anymore and not the whole comapny is burning). To save important data (a reason for a remote NAS), it maybe better to think about a data replication or a backup strategy to a remote location as using a real cluster.

Nevertheless your intension may be possible, if you have a very fast and stable conenction between your locations, cluster configuration are not intended to work in that way (in my mind).
You are looking at a geo cluster.
Hope you have deep pockets.

I have only ever quoted on this twice, and both clients said no when I told them the costs (over three years - well over 100,000 - put that in to any currency you like). You need to have a high speed, dedicated link between the sites. No VPN, sharing etc. The bandwidth requirement is very high. The hardware is also quite specialised.
Then you will need training or have to bring someone in to do it. Most of the suppliers of this will usually insist or pressure you to take consultancy.

I have never deployed one because I haven't found a client who could justify the outlay.

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