FreeNAS Mini Write Cache (ZIL) Upgrade Boost write performance and reliability on your FreeNAS Mini with a dedicated ZFS Intent Log (ZIL) device. Take advantage of FreeNASs advanced algorithms to hold critical data waiting to be written in the ZIL until confirmation of a successful write is received. Never lose data waiting to be written to ZFS, even in the event of power loss. Hardware tested and qualified by the developers of FreeNAS.