Re: Windows NFS was so terrible
Nexenta was never intended to front a SAN. That directly from my counterpart over there as a solution architect. Even though Compellant used Nexenta just that way, the guys who knew it best HATED it used as a SAN gateway.
Windows 2012r2 was actually pretty damned usable for NFS - I had a couple of large implementations of NFSv3 fronting Nimble Storage iSCSI SANS, they were performant and rock solid. Outperformed much more expensive NTAP systems Never tried it for V4, and at the time Nimble didn't have deduplication at all. No problems there, we weren't using the NFS for VMWare .vmdks as only a moron would do that when a well integrated block system is available.
Your issues sound like you might have been running out of inodes (dedupe COULD exacerbate that) and the inode limit for Windows based NTFS systems is not all that large. That would explain "out of space" when you have plenty of physical space - no addresses available to store the data. I've seen that in some largish Veritas FS environments.
WIndows NFS PRIOR to 2012r2 *was* terrible, but after 2012r2 dropped it was very usable for even some fairly high performance work loads with the right SAN mounted to the host. If you haven't tried it and tested it personally, spare me the hate mail...and I KNOW there are better systems out there for NFS. But Windows isn't the worst of it.