What are some alternatives?
When comparing Rockstor and Zentyal, you can also consider the following products
OpenMediaVault - OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux.
ClearOS - A very good alternative for Windows Server, for free
FreeNAS - FreeNAS is a storage operating system strong and robust enough to meet the needs of enterprise level businesses.
NAS4Free - NAS4Free is the easiest and quickest way to install an Open Source free NAS server. From home NAS to enterprise network storage, NAS4Free is trusted by thousands of installations every day.
NethServer - NethServer is an operating system for Linux enthusiasts, designed for small offices and medium...
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.