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Re: Clustering mail servers - Cyrus or Courier ?

On Sun, 5 Aug 2001 16:10, Przemyslaw Wegrzyn wrote:
> I'm looking for good solution for big, scalabale mailserver installation,
> for 500,000 accounts and more...
> As for now I think:
>  - sharng NFS-mounted mail storage is not so good idea.

Why not?  If you use Maildir storage then it's NFS safe.  If you use a NetAPP 
Filer, a VA NAS device (or any machine running 2.2.x kernel with LVM, Ext3, 
and appropriate NFS kernel-server patches as the VA NAS devices did), or some 
similarly powerful NFS server then performance should be more than adequate.

For Ext3 you need to keep the number of entries in a directory down to <1000 
for best performance, but most users don't have that many messages in their 
mail folder.  So you just have to do suitable directory hashing to make sure 
you don't have too many users in a directory (all mail storage software has 
support for this).

Then you give your NFS server multiple (at least 2) network cards for good 
bandwidth and for redundancy (connect each network card to a different switch 
- switches are cheap).

Then you have 2 mail server machines which may run POP as well or you could 
have 2 separate POP servers.  You have one server on each switch so that if a 
back-end switch dies you don't lose everything.

Then you can have multiple mail servers running at the same time for 
increased reliability.  This is much better than the Perdition approach of 
increasing the number of points of failure.  Having an NFS file server as a 
single point of failure is as good as it gets, making an NFS file server 
reliable is much easier than making a mail server reliable...

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/projects.html Projects I am working on
http://www.coker.com.au/~russell/     My home page

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