alexander benaguev wrote: > dual-master mysql as backend. set of dbmail-imapd or -pop3d at both > blades as frontend, which connected to localhost.
That's not advisable. Dual master/slave is OK, in which each node is it's own master and slaves the other. Simultaneous write access on both heads will give you problems though. For instance smtp injection on one head while the user is playing with his imap box on the other head will cause replication failures which require manual intervention - basically a manual transaction merge on both machines :-(. No fun. Better to let the imap, pop3 and smtp frontends connect not to localhost but to a specific ip number. You can use heartbeat to make this ip number highly available, in which each of your mysql nodes can take over from the other. It's just the reads that are concentrated on one head in this setup. The write load is replicated anyway. You might want to compensate for the read load inbalance with something intelligenter than round-robin. Or maybe something less intelligent, that is running some frontends specifically on the node which is /not/ currently the mysql primary. It's good to think about your goal here. High availability + data integrity (maximal uptime) leads to other choices than load balancing (maximal performance). Especially given relatively modest projected numbers of users, uptime maximalisation might make more sense than performance maximalisation. :*CU# -- *** Guido A.J. Stevens *** mailto:[EMAIL PROTECTED] *** *** Net Facilities Group *** tel: +31.43.3618933 *** *** Postbus 1143 *** fax: +31.43.3561655 *** *** 6201 BC Maastricht *** http://www.nfg.nl *** the central idea in military operations is effectiveness, not efficiency [ Wesley Clark, http://www.nybooks.com/articles/16650 ]
