2 month dredge but I thought the obscene RAM requirements for ZFS were only when using L2ARC & deduplication? Currently getting away with 2GB for a 24TiB filesystem on a backup node at work using zfsonlinux & centos 7. It is used to hold snapshots of 12TiB of rsync'd files.
Yeah, maybe it was just me. I have 24TB of disk, and that dictates RAM needs that change the parameters of everything else.