Keepalived has both functionalities in the same piece of code and uses one configure script.
Linux-HA uses ldirectod to handle realserver failover.
pf, the Open BSD firewall, is very well written and nicely designed. There are several packages available to do failover for LVS.
Some of them overlap in functionality and some of them are for different purposes. Failover of realservers occurs by changing the ipvsadm table on the director.
Here's an article on the high cost of delivering high uptime computer service by Steve Levin.
Others will setup LVS for you and administratively the two layers are not separable.For this level of reliability, the system has to handle all faults without human intervention. For service failure on the realserver or director failure (without the Server State Sync Demon), the client's session with the realserver will be lost.This is no different to what would happen if you were using a single server instead of an LVS.Other software is used in conjunction with LVS to provide high availability (i.e.to switch out a failed realserver/service or a failed director).The most common problem found is loss of network access or extreme slowdown (or Do S).