User  shows us some tips and tracks on how to use your SSD efficiently with the ZIL (ZFS Intent Log) feature of FreeNAS. Follow the link below for the full set of instructions.

ZIL and Cache

Not open for discussion; I think it is a complete waste of resources to use a 120, or 250GB SSD for logs, let alone cache, as FreeNAS will (and should!) use RAM for that. So, I searched and found a way to create two partitions on a single SSD, and expose these as ZIL (ZFS Intended Log) and cache to the pool.
Mind you – there are performance tests around, questioning the efficiency of ZIL and cache. I am not going to test this, I will just add ZIL and cache – I have an SSD especially for this purpose, but I am just mentioning the fact that the use case might differ for you.

The pool?

Erhm, in the mean time, I have created a pool, existing of two virtual devices, existing of 6 harddisks each. According to several sources on the interweb, this will deliver resiliance, as well as performance.

Full tutorial: http://vanbortel.blogspot.com/2017/07/storage-server-freenas-use-your-ssd.html