As you asking for the Hardware Requirements of the Freenas open Source the Hardware Requirements are given below :

Hardware Requirements

Multicore 64-bit processor

16GB Boot Drive (USB Flash Drive suffices)

16GB (ECC Recommended)

At least 2 direct attached disks (Hardware RAID strongly discouraged)

For best results, see FreeBSD Hardware Compatibility List for Supported Disk Controllers

Drives designed for NAS (such as WD Red drives) are recommended.

At least one physical network port (Intel Recommended)

Requirements for the Small and Medium Business is given below :

One to four Enterprise-class 64-bit multicore processors.
Two mirrored 16 GB Boot Drives (USB or SATA DOM recommended)

32GB ECC RAM Minimum (1GB per TB of storage is a good rule of thumb but might need to be adjusted depending on workload/application)

At least 4 direct attached disks (Hardware RAID strongly discouraged. It reduces the data protection and recovery features of FreeNAS considerably.)

Host Bus Adapters (HBAs) are recommended instead to give FreeNAS/ZFS direct access to the individual drives.

LSI HBAs are the best choice with FreeNAS.
For best results, see FreeBSD Hardware Compatibility List for Supported Disk Controllers

Enterprise quality SATA/SAS hard drives are recommended.

High-endurance Flash/SSD-based write log device (ZIL) for synchronous writes only (Flash/SSDs with “Power Loss Protection” recommended). Two devices mirrored if uninterrupted performance is critical.

High-performance SSDs for read acceleration if the most-requested data doesn’t fit in RAM and the random read load is high.

At least two physical network ports. Intel recommended for 1GbE. Chelsio recommended for 10GbE.