The best way to get the most out of a FreeNAS® system is to install as much RAM as possible. The recommended minimum is 8 GB of RAM. The more RAM, the better the performance, and the FreeNAS® Forums provide anecdotal evidence from users on how much performance is gained by adding more RAM.
Depending upon the use case, your system may require more RAM. Here are some general rules of thumb:
- To use Active Directory with many users, add an additional 2 GB of RAM for winbind’s internal cache.
- For iSCSI, install at least 16 GB of RAM if performance is not critical, or at least 32 GB of RAM if good performance is a requirement.
- When installing FreeNAS® on a headless system, disable the shared memory settings for the video card in the BIOS.
- To use ZFS deduplication, ensure the system has at least 5 GB of RAM per TB of storage to be deduplicated.
If the hardware supports it and the budget allows for it, install ECC RAM. While more expensive, ECC RAM is highly recommended as it prevents in-flight corruption of data before the error-correcting properties of ZFS come into play, thus providing consistency for the checksumming and parity calculations performed by ZFS. If you consider your data important, use ECC RAM. This Case Study describes the risks associated with memory corruption.
Unless the system has at least 8 GB of RAM, consider adding RAM before using FreeNAS® to store data. Many users expect FreeNAS® to function with less memory, just at reduced performance. The bottom line is that these minimums are based on feedback from many users. Requests for help in the forums or IRC are sometimes ignored when the installed system does not have at least 8 GB of RAM because of the abundance of information that FreeNAS® may not behave properly with less memory.