ext3 with maildir++ = huge disk latency and high load

[Andrey]

Hello,

I have a production mail server with maildir++ structure and about 250GB 
(~10 millions) of files on the ext3 partition on RAID5. It's mounted 
with noatime option. These mail server is responsible to local delivery 
and storing mail messages.

System has Debian Squeeze installed and Exim as MDA + Dovecot as 
IMAP+POP3 server.

Bonnie results are terrible. Sequential output for Block and Rewrite are 
10722ms and 9232ms. So if there is a 1000 messages in the mail queue 
load is extremely high, delivery time is very big and server can hang. I 
did not see such problems with UFS on FreeBSD server.

As I understand ext3 file system is really bad for such configurations 
with Maildir++ (many smaill files)? Is there a way to decrease disk 
latency on ext3 or speed up it?

With regards, Andrey