Svetozar Mihailov pisze: > Hello all, Hello Svetozar,
Sorry for the late response, but recently I've not had much free time to watch this mailing list. > 2.2 I do not want to use load balancer because if load balancer dies > everything stop. I will implement monitoring (ping?) daemon, which will > add/remove servers to dns if some of them dies. Is there recomended > minimal TTL for dns records in this case? Yes, it's true that only one load balancer is not good idea. Hence, you should have two redundant load balancers or second backup load balancer on the alert. In my opinion a load balancer is a base element of modern and high availability cluster in these days. Below is a short list of the most important advantages of the load balancer: 1. Network traffic load balancing My administrator experience is that DNS based load balancing sucks. It's not a blame of architecture of domain names system. It's because of stupid Windows hosts. They ignore setting of DNS TTL and cache resolved IP addresses, so you can't stop them to connect with your cluster nodes when you want to reboot them, for example. Of course, you can move IP addresses between machines, but I don't like that manual job. If you want to switch the network traffic when you upgrade a distro on one of your nodes or do some tests, then you should use some free load balancer. Your jobs will be invisible for your users! We use Keepalived in our clustered mail system and I can recommend it for you if you prefer Linux. 2. Security What do you do when some evil people make DoS attack on your cluster? Probably you drop or reject their IP address on all nodes of the cluster. Yes, you can do it in that way, but it's not quick and handy. If you have load balancer(s), then you can cut off aggressors on only one (or two) machine(s) and the problem is resolved. I hope it will be helpful for you or another Courier admins. My best regards, Pawel Tecza ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ courier-users mailing list [email protected] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-users
