A clear look at CIFS in Solaris by Alan Wright:
Many people assumed or desired that the Solaris CIFS server project would be like Samba but what would that achieve? Sure, it would avoid breaking any eggs, i.e. avoid making substantial changes to Solaris, but Samba is available on Solaris today. There is no point in creating another Samba. If you truly want an integrated CIFS implementation, that can really inter-operate with Windows at a fundamental level, the operating system has to support certain core features. Eggs will have to be broken.