FreeNAS is a free Network-attached storage (NAS) server. It supports following protocols:
=> CIFS (Samba) – Mac / UNIX / Windows can use CIFS to store files
=> FTP
=> NFS
=> Rsync
=> AFP
You can use local user authentication, and software RAID (0,1,5), with a web-based configuration interface.
It also features:
* Support for S.M.A.R.T
* Local and Active Directory user authentication
* Software RAID (0,1,5)
The FreeNAS website is: http://www.freenas.org/
What is Network Attached Storage?
In the mid 1980′s two computer companies independently started to work on ways to access files, over the network. These two companies were Sun Microsystems and Microsoft. The Sun Microsystems method, which was for their UNIX operating system, is known as the Network File System (NFS) and was subsequently implemented in almost all versions of the Unix operating system including Linux. The Microsoft solution (which they actually joint developed with IBM in the initial stages) became known as SMB (Server Message Block) but in later years was renamed as the Common Internet File System (CIFS). The general functionality of NFS and CIFS is very similar and with either installed on a networked computer it can read and write to the file system on another computer on the network.
This ability to use a remote computer (a fileserver) to store files led to many companies deploying large centralized NFS Servers or Windows Servers which were accessed by hundreds and maybe thousands of Unix workstations or PC clients. Users would then be encouraged to store all important files on these servers as the IT staff would back up the servers regularly and so back up the important user files.
With modern needs for multimedia storage combined with high speed local networks, a new kind of storage solution has appeared, Network Attached Storage or NAS for short. A NAS server is similar to a traditional file server in many ways, especially in respects to the hardware side of the server. But a NAS server is much more specialized than a traditional office or departmental server in that it only provides access to storage via the network. It is not designed to run other applications such as databases or email servers which other types of server might.
Source of this article:
http://www.learnfreenas.com/blog/about-freenas/
http://www.cyberciti.biz/tips/low-cost-home-media-file-server.html