> We have been running this particular setup for about a year
> now... I am happy with the overall performance, however when
> things break, they have a tendancy to break badly especially
> with MySQL's replication.
> We had a problem with our NFS store dropping out from under the NFS
> server* (the DBs were located on the same machine). This
> forced a hard restart on the server and when the server would
> come back up the replication in MySQL was broken between the
> master and slaves (the master had a different replication
> point than the slaves, the slaves were requesting a start
> position that didn't exist. The worst part is we didn't
> realize it initially until updates to users, etc weren't
> being seen on the slave servers). This forced us to down the
> local database servers (slave database servers). This did
> have the advantage of forcing vpopmail to look at the master
> server for reads and writes which was a nice fall back
> position, but the restoration process was difficult and
> depending on the amount of data in the vpopmail database,
> very time consuming moving massive database dumps to resync
> the databases on the slave servers.
> I have had to do this process about 5 times since we have
> started running this setup. Also if you are going to do this,
> be sure that when you do a mysqldump of your data (you are
> doing that nightly right?;) ) be sure to use the
> --master-data option so the slaves will know where to pick up
> replication with the master. Another tip... Turn off auth
> logging to mysql if you are doing replication... ICKY.
Thanks for the info!
How do you find NFS performance? (Did you use any special tweaking/mount
And what are you using for auth?(NIS/LDAP etc)
> We are currently looking at a load balancer solution
> (UltraMonkey/LVS or Foundry ServerIron,
I would like to consider a Linux alternative, but majority of our
support staff are not Linux savvy...
> still haven't decided
> but UltraMonkey/LVS is working well so far) with DRBD
> (http://www.drbd.org/) and heartbeat for both the database
> and NFS servers and cheap clones as the actual mail servers
> running a combination of qmail+vpopmail+clamav+spamassassin.
Just out of interest - What are you using to sync data(configs etc) -
You also mention NFS "servers"...So I assume you are running more than
one behind a loadbalancer...how are you synching data between them?