Load sharing techniques

[Joey Casas]

I am new to this list but have been working with MailScanner for a few years now. With the recent (re)uptick in spam volumes, and increased rules to cope with new techniques, we are having general performance "problems" with our current hardware. Mainly, increased queue size and associated delays during peak times.

Currently I have a basic round robin setup between three MailScanners and two external IPs that forward to all servers. I might be getting more "mediocre" hardware soon and I _can_ simply add them to the NAT pool. However, the servers are all of different capabilities and generally I have one or two servers that accumulate larger queues than the others. Average mails per second are very similar (MS1 .69, MS2 .74, MS4 .75).

I also have some pretty fast RAID 5 disk that I can NFS or iSCSI mount - which leads me to my question. Has anyone done a "shared queue" setup where multiple servers look to the same mqueue to scan and what problems could be foreseen? I imagine maybe file locking, header accuracy, etc...

Thoughts, or concepts I might read up on?

Thanks for any input!
Joey Casas
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