[Catalyst] FW: Clustering catalyst apps

[Matt S Trout]

Gert Burger wrote:
> Thanks for the reply, here are some of my comments on this:
> 
> Using round robin dns still means that if 50% of the servers are down,
> 50% of all queries will goto the broken machines. Which will piss of
> half your customers.
> 
> I have looked at the High Availability systems that have been written
> for linux and they provide doubles(Or more) of everything, from load
> balancers to db servers. The issue I have with them are they require a
> great deal of money in hardware to get running.

Not really, if you're buying a fair few at once people like Dell will do 
you pretty damn good deals on moderate 1u servers if you're buying a lot 
of them at once.

In the end though, you're probably going to have a single point of 
failure somewhere - e.g. "we have two of every piece of kit but only one 
backup generator for when the UPSen run out", or at the very least 
"there's only one planet earth so if there's an extinction level 
asteroid strike ..." :)

The point here is to push that single point of failure back as far as is 
cost-effective. For a small company, making sure your border router is 
bloody good and using two servers with a single service IP and failover 
is often good enough.