[SchlingBlade]

I wish I still had access to the Zimbra system I put in at a wireless ISP about a year ago so I could pull some stats. It was on a Dell 1950 w/dual 3.0Ghz dual-core Xeons (HT disabled), mirrored 300GB SAS drives, 4GB of RAM, ran Ubuntu 6.06 LTS 32-bit (32-bit Zimbra), and served a very busy 4500 customers. No problems with RAM usage, rarely hit swap. It sent and received somewhere around a million messages a day.

I wanted more RAM for the system, and even more drives, but the boss said no. At any rate, it turned out to be MUCH more dependable than the Windows based email system it replaced, which was on better hardware with more RAM.

My home Zimbra system (Open Source) is on a machine with a dual-core AMD Athlon64 X2 3800+ processor, 2GB of RAM, mirrored 160GB SATA drives (software mirroring), Ubuntu 6.06 LTS 64-bit (64-bit Zimbra) and never hits swap. I have about 30 user accounts on that system right now, and will be adding more as time goes on. (This system feels much faster than the Dell 1950 system ever did, even with no users/load on the Dell system)

I agree, 2GB is the minimum you would want for any type of environment. 4GB will do OK, but I've seen that not be enough in a couple cases. 8GB seems to be the sweet spot, but make sure you are on a 64-bit system. Multiple cores/cpus will really help as well. Running Zimbra in a VM for production isn't ideal, use a real server when you deploy for production. Drives don't matter as much, as long as they are reliable and in a good RAID configuration for redundancy.