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Re: Load sharing POP/IMAP/smtp

On Thu, 6 Feb 2003 06:28, Lauchlin Wilkinson wrote:
> does anyone have any good links/info on how to set up a
> loadsharing/redunant mail servers (pop, imap, smtp).  At the moment I
> have 1 server doing all three jobs but we are soon going to grow out of
> this arrangment andI have not had any experience with setting up such
> systems.

Load sharing and redundancy are two totally different issues.

If you want redundancy then the best thing to do is get a pair of NFS attached 
storage devices running in an an active/standby configuration and have the 
SMTP/POP/IMAP servers mounting the storage by NFS and using Maildir storage.  
This will cost huge amounts of money.

For load sharing I've got Dell 2650 servers with 2*1.8GHz Xeon CPUs, 4G of 
RAM, and 5*72G U160 hard drives (4 in a RAID-5 and a hot-spare) that each run 
200,000 email accounts with Qmail for delivery and Courier IMAP and POP 

At the front end I have Perdition for directing the POP and IMAP to the right 
server based on LDAP data (NB the current version in Unstable still doesn't 
work properly for this - the next version should do it).  Also I have front 
end Qmail servers which direct the mail to the correct back-end server based 
on LDAP.

For typical ISP use you should be able to handle at least 100,000 users for 
SMTP, POP, and IMAP on a single box without any significant problems (and 
it'll be much easier than installing Perdition etc).  I could setup a single 
machine to handle 1,000,000 accounts if required, it would be an expensive 
machine, but setting up a number of smaller machines with Perdition etc is 
also expensive and has management costs too.

http://www.coker.com.au/selinux/   My NSA Security Enhanced Linux packages
http://www.coker.com.au/bonnie++/  Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/    Postal SMTP/POP benchmark
http://www.coker.com.au/~russell/  My home page

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