Reading up on Exchange server sizing, most of the guides are aimed at scaling for corporate Outlook users, so I wondered if I could pick someones brains? Especially with regard to RAID setup and disks
The server will be just a mail server.
Running Exchange 2003 or 2007 + av & spam filtering (double-checking rbc filtering, rather than primary filter). It'll also be providing remote access to mail via OWA.
940 mailboxes, 870 of which will be accessed via OWA only, the rest a mix of Outlook and OWA. Up to 300 users in school could use mail at the same time.
Out of school, I'm not sure about - we have 90% of kids using Moodle while at home, so chances are they'll be looking at email regularly as well.
I prefer Dell (everything else is), but not a deal-breaker.
Dual cpus - I know exchange can make good use of them, needed?
Disks and RAID setup - not sure, a corp guide for a "small" (100 users) server was:
OS and Exchange Software on a RAID 1 (would do anyway)
Database on a separate RAID 5 or 1
Transaction logs on another RAID 1
Unless you're running hundreds of message / minute you don't need to worry too much about putting your transaction logs on their own RAID-1. partition the system drive into two logical drives and stick the transaction logs there instead. Databases would be better on a RAID-5, but it's more important to make sure your drives are large enough to handle the users you've got. 3x145GB SAS drives would probably be fine for your databases - it'll give you about 200MB per mailbox.
go for a single dual-core CPU rather than two seperate CPUs, just to save money. core2Duos (or the Xeons based on them) would be best. 2GB memory will be fine.
Our first exchange server was a poweredge 700, P4 2.8, 1GB RAM, 3x250GB hard drives in one RAID-5 set. It served about 600 mailboxes without ever breaking a sweat.