Question: Does anyone know if I can install normal 2.5" SATA drives inside an HP DL360 G5 server? Right now it has 6 72GB SAS drives. I am looking for raw storage for my files SAS performance in not required.

Answer: 
SATA2 disks should be compatible with the Smart Array P400i that comes with your server (or any other SAS controller, for the matter), although probably not with stellar performance as others have noted. But keep in mind that not all SATA disks are suitable for use with RAID because of the infamous Time-Limited Error Recovery parameter (TLER for WD drivers, also called ERC by Seagate and CCTL by others). Disks not prepared for RAID configurations will frequently drop from the array.
You can use SATA drives, but make sure they are "raid edition" drives intended for use in servers, and not drives intended for use in desktops. "Raid Edition" is Western Digital's name for it: other vendors each have their own name, but this is important; it's not just snake oil and you can run into problems if you get cheaper disks.

Expect to spend about $100 for a 1TB disk of this type:  

[http://www.amazon.com/Western-Digital-Cache-Enterprise-Drive/dp/B001IEXU68](http://rads.stackoverflow.com/amzn/click/B001IEXU68)  

or $120 for a more recent version with a larger cache:  

[http://www.amazon.com/Western-Digital-Cache-Enterprise-WD1003FBYX/dp/B003SANWI6](http://rads.stackoverflow.com/amzn/click/B003SANWI6)