on 3/13/09 9:54 PM, Robert Hajime Lanning said: > On Fri, 2009-03-13 at 20:26 -0500, Brad Knowles wrote: >> For example, putting NTP time servers behind load balancers >> are a really bad idea. > > The only real issue with load-balancers, is with applications/clients > that keep server state, outside of a single transaction. Since the next > transaction could be on a different server. > > With the NTP reference above, the NTP client keeps offset/jitter > information about each server (based on IP) that is references. So, > unless the server pool is in EXACT lock step time synchronization, the > clients will see a large jitter factor for the cluster IP.
No, that's not the only problem. If just one server behind that load balancer goes whacko, then all clients which contacted it through the load balancer will mark the load balancer as bad, and will never use anything through the load balancer again. NTP already has built-in techniques for auto-discovery, reducing load to servers, balancing load, high availability, etc.... You shouldn't try to defeat those and destroy the very basis for the NTP protocol by putting NTP servers behind a load balancer. Same deal for doing NTP to IP addresses that are distributed via anycast techniques. But that is just an example of how you have to understand the nature of the protocol and how it's used, before trying to put servers for that protocol behind something like load-balancers. Obviously, LDAP != NTP, but there may still be some subtle issues that need to be considered when you're looking at particular solutions, and the only people who might know what those subtleties are would be the experts on the mailing lists, etc... for the application in question. -- Brad Knowles <[email protected]> If you like Jazz/R&B guitar, check out LinkedIn Profile: my friend bigsbytracks on YouTube at <http://tinyurl.com/y8kpxu> http://preview.tinyurl.com/bigsbytracks _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
