2012 R2 + SMB3?

OK, so it looks like the real source of this problem is lack of support for "virtual hard disk sharing." Articles that talk about the specific error, "The storage where the virtual hard disk is located does not support virtual hard disk sharing" are vague in what this actually means. One article specified this is a feature of SMB 3.01, another mentioned 3.02, but my VNXe's connection is identified as 3.00 and it works, so I'm not sure.

In case anyone else wants to try or wants to just add a hidden administrative share, here's what you do:

I faked an administrative share by connecting through SSH and modifying the /etc/frontview/samba/Shares.conf file. It's a standard config file for Samba, so I just added a block that looks like this

[c$]
path = /MY_VOLUME/parent
comment = "fake admin share"
guest ok = 1
admin users = "admin","DOMAIN\administrator"
writeable = 1

Below that, a block containing the destination share within parent

[vm]
path = MY_VOLUME/parent/vm
comment = "destination"
guest ok = 1
admin users = "admin","DOMAIN\administrator"
writeable = 1

Make sure you create the folders specified by "path" if they don't already exist.

I also created one to the root of my volume just so I could set permissions on the administrative share itself. This didn't help. The ReadyNAS follows Samba's rules and share$ is hidden, everything behaves as expected. Your entire configuration is overwritten whenever you save through the web console and there's no guarantee that an upgrade won't wipe this out.

The Samba version on the ReadyNAS is 4.0.13, so it's pretty new and 4.0.14 doesn't seem to address these issues. This is clearly not going to work but I'd love a better idea of what's missing. This would be a great thing for the 4220 to support!