Am 02.05.2011 22:38, schrieb Paul J Stevens: > On 05/02/2011 09:09 PM, Reindl Harald wrote: >> >> Am 02.05.2011 20:14, schrieb Jesse Norell: >>> Not currently, I hadn't even thought of HA/backup db issues > > For mysql there's mysql-mmm.org. Works really great for managing HA for > mysql clusters. Doing just what Harald appears to need.
sounds interesting but i would dislike too much layers because overhead, possible errors difficult to debug if something goes wrong for the mail-system most important is postfix and directly involved daemons for a failover because you have the new message fully received and on local disks - form this point the sender is ready, message delivered and a "postque -f" enough to deliver after correcting a problem on the backend if we are speaking about spear the load on more than one machine split read/write would solve performance problems in the most cases since reads are the biggest part and if you have two machines with half read-ueries each of them the load is much differenbt than one machine with all requests saying we have 3 servers: * configre all 3 in the app * same user/pwd * the app have only to konw "spread reads" * if a new connection is needed take a random host * if one host is not reachable take random another one * voila you possible won the whole game mypoint for the policyd is simplay that the in postfix included failover will be broken since if the policyd can not connect to the database a tempfail in postfix happens maybe someday in dbmail spread read/write makes sense too but here also i would prefer to not include another sofwtare layer * writes always to the master * if configured using a read-connection pool * choose one of the existing connections from the pool at the begin of user-connect * if it is dead, choose another one of the pool * perfectly let the pool-child connect again randomly to one of the available hosts
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