This is a compact NAS for raspberry pi and one 2.5 storage drive. I designed this for my raspberry pi B+ using Tinker cad, this will most likely fit other RPi however i dont have any others to test. There is and area on the rear of the NAS for a cpu fan to provide some airflow. my raspberry pi rarely gets hot running as a nas but i added one anyway.
The operating system i am using for the NAS is Open Media Vault: https://www.openmediavault.org/
Powered USB HUB: https://goo.gl/J6iCNy
2.5 storage drive
SATA III to USB: https://goo.gl/Xey44u