[Dovecot] Virtual Servers

[Daniel L. Miller]

Maybe a little off-topic - but I hope not too much.

Looking for some insight on setting up Dovecot under a virtual server.  
In particular, I use VirtualBox - and at the moment, Ubuntu Linux.

Initial questions on configuration:

Caching.  It seems to me - and I'm probably wrong - that running a Linux 
in a VM on a Linux host, there would be a duplication of caching.  That 
is, the host server has a file cache - and the VM, which is otherwise a 
standard Linux installation, is also going to try to cache its files.  
This strikes me as a duplication of effort and waste of RAM.  Is this 
something I should devote any time to thinking about and trying to 
minimize?  If so, how?

Mail storage.  My current mail store is a RAID-10, using the mdbox 
format.  I wish to continue storing the mail on "raw" disks - not place 
the mail inside a virtual disk.  Accordingly, the VM needs to reach the 
mail outside the VM environment - which according to conventional wisdom 
means NFS.  My initial testing shows NFS results in a dramatically 
reduced performance for Dovecot.  Given that this NFS access is going to 
be exclusively for Dovecot, and I'm only running a single server, are 
there any NFS or Dovecot tweaks I should implement?  Is there an 
alternative connectivity for the VirtualBox environment I should explore?

-- 
Daniel