If you're looking to utilize 20 drives, I would consider an external RAID enclosure and an enterprise class controller card. What is the use of the storage? Is performance important? What is your budget?
Why enterprise class controller for a home server?
Here are low cost, low power, easy to built.
1) FreeNAS solution feature:
- Each SATA port can be 15TB volume with 3TB hdd.
- Low cost, headless
- Stream media, network back up.
Look at here url=http://www.tomshardware.com/forum/265641-32-40tb-server-performance-issue]40TB
Home Server base on FreeNAS
2) WHS and SnapRAID solution feature
Drive extend - Volume can grow as need it, no hdd size discrimination, data is protected.
Low cost with port multiplier solution
Both solution can be use with Green drive (5400rpm) to save money and electricity.
If you are interest of how to let me know, i will post the way that I build
Edit: headless means NO K/M and monitor just the box