You can google it as there should be plenty of discussions. Even on HN using 1GB of memory for ZFS. [1] The two ZFS memory intensive feature is ARC ( Cache ) and De-Duplication.
The 2nd thing is that you are not using the NAS / DAS frequently in this scenario. The memory only get you extra performance. The only reason why you want ZFS is file integrity.
[1] https://news.ycombinator.com/item?id=11897571