StableBit DrivePool - State of the art, file based drive pooling software.

PetaSAN - PetaSAN is an open source Scale-Out SAN solution offering massive scalability and performance.

btrfs - Btrfs is a modern copy on write (CoW) filesystem for Linux aimed at implementing advanced features...

Amahi - Amahi is a media, home and app server software known for its easy-to-use user interface. Amahi has the best media, backup and web apps for small networks.

Greyhole - Greyhole is an application that uses Samba to create a storage pool of all your available hard drives, and allows you to create redundant copies of the files you store, in order to prevent data loss when part of your hardware fails.

XigmaNAS - File Sharing, OS & Utilities, and Security & Privacy