Trying to spec out a server for 2000 users, possibly upwards of 3000 in the future. Looking to create a server on a tight budget, using refurbs. 

My problem? Storage has gotten really, really expensive--Especially SSDs and while we do use smartermail and I would wager we generate email volume comparible to 400 users on our 100 user server, I have no idea what I would need for 2000 users.  In particular, I want to see if anyone has had success doing so using spinning disks over a SSD.--Getting a small SSD pool for the spool and the OS isn't a problem, but getting enough within budget to store the users data might be.

I was thinking about putting together a server using 10-16 10k SAS drives in a RAID 10 configuration and 32gb of ram and 16 cores via buying a refurb Dell 730xd and run Debian + Smartermail, but wanted to get input from the community.

The amount of drives would be less for the storage, and more to increase the IOPS needed.