DNS Round-robin, Load Balancing, Load sharing, and failover in 2012

Question

I have been reading many posts on serverfault as well as on other sites regarding all these.

What I understand is, Multiple A records(round-robin dns) can be used for both :

• Load sharing (round-robin, but NOT load-balancing). Many people say that “Load Balancing” but I think there will be no load-balancing because “Balance” means (literally) “compare two(or more) and adjust” (and that is what Real s/w or h/w Load balancers do) but Browsers never do this, instead they randomly select an IP and connect to it. It doesn't have any knowledge about the current load of that server (probably, the IP it picked had the highest load!).

• Automatic failover (latest browsers only). Yes, I think DNS can be used as a simple failover system (at least in 2012, I dont know when it actually "came in effect"). please refer to : https://webmasters.stackexchange.com/questions/10927/using-multiple-a-records-for-my-domain-do-web-browsers-ever-try-more-than-one and Browser-based DNS failover using multiple A records and http://www.nber.org/sys-admin/dns-failover.html

I would like to make sure my assumptions/findings are right. So let me know please.....

Answer 1

If you want real load balancing for web server's than you should think about Haproxy . It has high efficiency using reverse proxy and failover system (keep alive & Heartbeat) Haproxy load balancer will work as a front end server for your web server.

To know more about Haproxy you should read http://haproxy.1wt.eu/download/1.2/doc/haproxy-en.txt and http://www.howtoforge.com/high-availability-load-balancer-haproxy-heartbeat-fedora8

Answer 2

In Load-Sharing we share the traffic across multiple paths, even if it is in an unequal fashion. Load balancing is used to achieve network efficiency. It distributes the traffic in an even manner across a network which has multiple-paths, this is done to get optimal resource utilization, maximize throughput, and minimize response time. So these two are really different things. round-robin when used with DNS(domain name server) is a method af load balancing although it has a drawback that it does not reports automatic failover of a node,even then techniques exist by which round robin technique can be improved.