Hi all, We've had very good success with LVS/heartbeat/ldirectord balancing web servers from a pair of redundant balancers (running centOS 5). I've never tried it with LDAP but it looks well-supported. There's quite a bit of documentation at http://www.linuxvirtualserver.org and http://www.linux-ha.org .
In a nutshell, LVS does the balancing, heartbeat monitors the balancers, and ldirectord monitors the real servers for availability. There's a bunch of different options available for balancing algorithms and health checks. Piranha is another option from Redhat as a replacement for heartbeat/ldirectord, I haven't tried it. If you have multiple balancers (maybe in separate locations) a connection interruption between them can cause them to both become active, heartbeat has some solutions for STONITH (Shoot The Other Node In The Head) http://www.linux-ha.org/STONITH Jonathan On Jan 13, 2009, at 7:57 PM, Atom Powers wrote: > Please sir, can I have some more? > > I see two strategies emerging: > * Internal load balancing: let the servers negotiate between each > other to determine which one should service the request. aka linux- > ha, carp. > But a pretty serious problem occurs if one or more of the servers > fails in such a way that it thinks all the other servers are down > and all the other servers think that it is down. I would rather not > leave it up to the servers in the cluster to decide if they have > failed or not. > > * External load balancing: use a proxy or router to balance requests > among a cadre of servers. aka F5, pf rdr rules, ipvs/lvs. > But how do you make the load balancer highly available? A hardware > load balancer will be more stable than any server, but it can still > fail. > > ipvs/lvs hasn't been updated since 2004 (the FreeBSD port was last > updated in 2005). While that might indicate a mature project, I'm > skeptical; especially given the amount of work that has gone into > other networking projects since then. > > linux-ha/heartbeat looks interesting, but sounds like it could be > very suceptabe to the situation where more than one server thinks > that it should be the only server. > > I can build a pretty simple, and moderatly robust, load balancer > using carp, pf, and router-side scrips which should do nearly the > same thing as a layer-7 router. This seems like my best option at > the moment. (It doesn't *have* to be open source, but my CFO would > appreciate it.) Unfortunatly pf, as near as I can tell, doesn't do > weighted redirection and would require scripts, and associated load, > to manage the IPs in the cluster. > > -- > Perfection is just a word I use occasionally with mustard. > --Atom Powers-- > _______________________________________________ > Tech mailing list > Tech@lopsa.org > http://lopsa.org/cgi-bin/mailman/listinfo/tech > This list provided by the League of Professional System Administrators > http://lopsa.org/ _______________________________________________ Tech mailing list Tech@lopsa.org http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
