> 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?


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