hardware recommendations for MURDER?

[Marten Lehmann]

Hello,

I have the same considerations for an upcoming cyrus murder setup. I 
would like to continue to use RHEL on HP ProLiant hardware as most of 
our services are running on it and it works perfectly.
While I understand that MUPDATE and the frontends will be idling around 
most of the time (I think I will use DL360 with Opteron DC or so) and 
I'm just not sure how much memory I should give them, I'm not sure about 
the backend hardware.
I'm a bit afraid of large systems, because if I have a server with 2 TB 
of storage, but it can't handle enough concurrent connections, then I 
won't be able to use the storage available and I have to setup an 
additional backend server with a lot of storage left unused. How can I 
calculate how much CPU and memory I need for an average user with a 
maximum of 100 MB per mailbox and some larger mailboxes like 2 or 5 GB? 
Would you prefer a really fat system with 16 GB of RAM, 1 TB storage and 
two dual core Opterons or two separate systems with 500 GB storage, 2-4 
GB RAM and one dual core Opteron? I would tend to the latter one (two 
small systems should be more failsafe than one large, aren't they?). So 
for the hardware I'm tending between a small DL360 with two big SCSI 
discs or a big DL385 with 6 drive bays.

Regards
Marten