On Thu, Feb 07, 2013 at 11:34:43AM -0500, S Ahmed wrote: > Thanks Willy. > > On the same note you said not to run anything on the same machine, to lower > costs I want to run other things on the haproxy front-end load balancer. > > What are the critical things to watch for on the server so I can be > notified at what point having 2 things on the server are becoming a problem?
First, you need to ensure that the machine never ever swaps. This is absolutely critical. The second important point to consider is that you don't want another process to use a lot of CPU on the same machine, or you want to dedicate some CPUs to other processes. And last point is that you don't want other processes to harm the network stack (eg: eat all the source ports by doing nasty things such as connecting and closing as a client, rendering the source port unusable for doing real work for 2 minutes). There are people who live very well with their LB doing several things, but the ones who do it without taking much care can really regret it. After all, the LB is the point where *all* your traffic passes, you certainly don't want it to slow down because a stupid process was started on it by accident. And some web sites can lose so much per minute of failure that they don't want to risk mixing workloads to save a $500 machine ! Regards, Willy
