FreeNAS do seem to recommend ludicrous minimum amounts of RAM, even without dedupe. If you ferret around their forums there seems to have been some history of data loss on low RAM machines. I don't know if it's something they've introduced but I've not seen mention of similar issues around the FreeBSD forums.
If you compare with the FreeBSD guide to tuning ZFS, they recommend 1GB and up and give settings for tuning for 768 MB. They mention that in practice dedupe would like upto 5GB / TB, so I've never bothered. 99 out of 100 don't need dedupe anyway - compression will be better.
I've never had an issue running FreeBSD + ZFS on a 1GB machine, which was my file server for several years. I ran FreeNAS with 1GB for around a year without issue. I'm now running a HP microserver with 16GB which gives 12GB to ARC.
If you compare with the FreeBSD guide to tuning ZFS, they recommend 1GB and up and give settings for tuning for 768 MB. They mention that in practice dedupe would like upto 5GB / TB, so I've never bothered. 99 out of 100 don't need dedupe anyway - compression will be better.
I've never had an issue running FreeBSD + ZFS on a 1GB machine, which was my file server for several years. I ran FreeNAS with 1GB for around a year without issue. I'm now running a HP microserver with 16GB which gives 12GB to ARC.