dovecot, maildir, UFS 2 performance

[Laszlo Nagy]

I need to install a new server. Primarily it will run apache + PHP + 
PostgreSQL. Its main task is to serve several websites, and provide web 
based admin interface for OLTP. The server will have 2xSAS disks in RAID 
1 for the base system and 10xSATA2 disks in RAID 1+0 for the rest. The 
SAS pair will only have 150GB space. The RAID 1+0 array will be above 
1.5 TB. I already have a good idea about how to tune PostgreSQL: log 
files go to SAS and data dir goes to SATA.

The secondary task for this server is to be an IMAP and mail server. We 
will be using dovecot, and shared maildir folders with ten thousands of 
messages. I'm not sure where to put the maildir folders, and what 
options to use for the filesystem. Dovecot wiki is not talking about 
UFS, only ext3, reiserfs and xfs:

http://wiki.dovecot.org/MailboxFormat/Maildir

Can you tell me some basic idea about how to configure this? I have some 
ideas but they may be competely wrong:

#1 maildir stores each message in a separate file. I think I need to 
dedicate a separate disk slice for maildirs and decrease block size on 
it. How big should the blocksize be?
#2 searching in messages is a common operation. Possibly read speed is 
very most important. But since there will be thousands of files to open, 
seek operation is also important. On which RAID array should I put mail 
dirs? Small SAS or bigger SATA array?

Thanks,

  Laszlo