Windows 2000 network file sharing is based on the traditional Microsoft networking mechanism of server message blocks (SMBs). UNIX systems, on the other hand, use the Network File System (NFS)—originally developed by Sun Microsystems—to share file systems across the network.
Until the original release of SFU, only third-party NFS solutions were available for Windows systems that needed to be able to share file resources with UNIX systems, and most of these solutions were expensive and problematic. The biggest issue was their inability to keep up with Windows NT service packs, which seemed to break these NFS solutions more often than not. In addition, these solutions often had significant performance problems. The Client for NFS, Server for NFS, and Gateway for NFS included with SFU version 3.0 resolve most of the problems and provide an excellent resource for using NFS in your mixed network.
However, several powerful SMB-based UNIX solutions address the problem of sharing file resources between Windows NT and UNIX. These SMB solutions vary in cost from free to expensive and support native Windows networking at either the workgroup or domain level. With the release of Windows 2000, only time will tell how well these solutions will keep up with the changes in the Windows 2000 security model as compared to the Windows NT model, but currently only Samba appears to be making any strides toward supporting the Active Directory service.
Originally, NFS was designed to run as a broadcast protocol using User Datagram Protocol (UDP). This protocol created substantial performance and network traffic issues for those intending to implement large amounts of NFS networking and made it difficult to share file systems across routed boundaries. Eventually, the NFS standard changed to support TCP for NFS networking, and virtually all modern clients and servers support this mechanism. However, some older NFS implementations still out there don't support TCP, so the default mechanism for SFU Client for NFS is UDP.
The biggest issue that the SMB-on-UNIX crowd has to deal with is the changing Windows 2000 security model. Two mechanisms are used for handling security with the SMB-on-UNIX solutions—workgroup-level security and Windows NT 4 domain-level security.
Workgroup security suffers all the same problems as workgroups in the enterprise environment: it becomes more difficult to manage as the number of users and machines increases, and it has limited options for actually managing security. However, workgroup security has a definite place in the smaller environment, where it's easy to understand and simple to set up. Plus, there's a nice cost advantage—a widely available and well-implemented freeware SMB server called Samba is available on virtually all UNIX platforms. Samba can also run as a Windows NT 4 primary domain controller and can authenticate users against a Windows 2000 domain as long as the Windows 2000 domain is running in mixed mode; Samba does not yet support Windows 2000 running in native mode. Other commercial, workgroup SMB servers are also available that run on a variety of platforms. They tend to be more Windows-like and easier to set up and administer than Samba, which shows its open source heritage.
Windows NT 4 domain SMB servers are also available from a number of UNIX vendors. All of these (except Samba) are based on AT&T's initial port to UNIX of Microsoft Advanced Server technology. Each is limited to running on the platform for which it was designed, and each has slight differences because the port from AT&T required tweaking in most cases. All of these UNIX SMB servers can be either primary domain controllers or backup domain controllers in a Windows NT domain, but all have problems dealing with the new security model in Windows 2000. Because these servers are based on the Windows NT 4 security model, you'll be forced to stay in mixed mode.
The UNIX SMB domain servers do have one important advantage over the Samba and SMB workgroup servers: to the users and administrators of the Windows network, they all look and feel exactly like a native Windows NT 4 server. The familiar Windows NT Server administration tools are used to manage them, and servers and shares look exactly like a Windows NT server to users, eliminating training and user interface issues. SFU version 3.0, discussed later, also provides a well-integrated solution that looks and feels comfortable and familiar to Windows users and administrators.