Jens Frank wrote:
I took the number "90%" as an example. You can make it 99% if you like, the result remains the same: One loadbalancer in front of two webservers reduces availability. Simple maths.
Simple but wrong maths, though.
The key is that the "availability" we're talking about is a function of what a given machine is doing. Individual webservers are likely to become unusable for many reasons -- apache problems, unbalanced traffic, etc. But the loadbalancer is nearly bulletproof.. and shields the user from failures of individual webservers in the cluster!
--Jimbo