I am struggling to find this solution...
Dell customer support is not helping with this issue. They are asking money for the support. I cant get any info from google regarding the configuration.
It is just windows 2008 underneath. Without AD it'll work but you'll have to sync local passwords up manually and some features eg. domain based DFS will be unavailable.
The Dell NX300 uses Windows Storage Server 2008. Storage Server doesn't need to be joined to a domain to work, so there's no reason it can't run without active directory.
As JamesRyan mentioned, you'll be using local authentication on the NX300 then (likely a pain) or have to use some other method for authentication.
Features like SMB/CIFS file sharing and FCI will work, but you will lose domain-dependent technologies like DFS.