What are some alternatives?
When comparing FreeNAS and Rockstor, you can also consider the following products
OpenMediaVault - OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux.
Amahi Home Server - 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.
Zentyal - Linux directory, domain, mail, gateway and infrastructure server for SMBs.
unRAID Server - A scalable, consumer-oriented, server operating system.
Unraid - Simplicity. Flexibility. Scalability. Modularity. Unraid empowers you to build the system you’ve always wanted using your preferred hardware, software, and operating systems.
ClearOS - A very good alternative for Windows Server, for free