Hi Dario,
if you have the money and the ressources to maintain, use two servers, one for the database with lot's of RAM and another one for the AOLserver.
For the database server (also true if you only go with one server):
- Dual Processor (I'm highly satisfied with Opterons, but that may be too expensive)
- 4GB of RAM, or more (that's what we use on aiesec.net, so far it is enough, but less is not recommended).
- Multi Channel SCSI RAID with fast harddisks. Take a lot of harddisks, that are fast and can be accessed simultaneously. We use a two channel setup with two mirrored harddisks each and strip across both channels. This reduces your harddisks from becoming the bottleneck. Maybe SerialATA is a better alternative though.
As for the server for AOLserver, you can use any computer, though you'll need quite some storage space for your users files. OTOH, "quite some" still does not fill up our 250GB RAID, therefore it is all a matter of perspective.
Last but not least, think about backups. You will need to backup your database along for all the files in the content-repository (I'd not recommend storing content in the database, but use the filesystem based version). Unless you have a central backup storage at your university, get a (cheap) different computer with lots of harddisk.
