CIFS Code Opened for Windows File Sharing

OpenSolaris and Windows can cooperate thanks to released CIFS code

Sun Microsystems Inc.'s recent donation of source code that implements the Common Internet File System (CIFS) protocol to the OpenSolaris project will enable Windows users to store and retrieve files on an OpenSolaris system, according to a key member of the company's CIFS engineering team.

The move will make CIFS a "first-class citizen" in the Solaris universe, and Solaris a stronger storage platform. CIFS (formerly known as Server Message Block, or SMB) is a file-sharing protocol for Windows clients, says Alan Wright, senior staff engineer on Sun's CIFS engineering team. It defines a standard for remotely accessing and transferring files across a network. Sun's CIFS Server is an in-kernel implementation of the protocol that integrates it with Sun's ZFS file system and the Network File System (NFS), which is the Unix/Linux equivalent of CIFS, Wright explains.

Native Solution
To support the CIFS protocol, Sun made changes to core components of OpenSolaris, Wright says, including the ZFS, the virtual file system (VFS), credentials and file-system utilities, among others. All of these changes were included in the donation to the OpenSolaris project.

"Native Solaris CIFS provides an integrated solution, which is designed to work with existing OpenSolaris utilities and services to simplify administration," Wright tells RDN. "It's not an application running on Unix providing access to Unix files; it's a native solution for sharing files to CIFS and NFS clients."

CIFS Server can operate as a member of an Active Directory domain, or as a standalone system in a workgroup, Wright says. Its ID mapping services provide multi-protocol support designed to allow local users and users of NFS and/or CIFS clients to share files transparently using a single, unified, active-control list-based security model.

"The CIFS Server will provide ubiquitous, transparent file sharing for Windows, Mac OS and other CIFS clients," Wright adds. "All of the benefits of OpenSolaris ... become available to Windows developers, including ZFS pools and snapshots for simplified storage administration, easy data recovery, data replication and unparalleled data integrity, scalability and reliability. Windows interoperability makes OpenSolaris a viable, attractive and potentially unrivalled server and storage solution for Windows users and Windows environments."

OpenSolaris vs. Samba
Sun's code contribution is a good strategic move, says Forrester Research Inc. analyst Michael Goulde, and one that's likely to benefit developers. "Microsoft has long sought to displace Sun from its accounts," Goulde says. "In order for Sun to maintain a presence, it needs to interoperate as well or better than Microsoft. And, if it can be more interoperable than Linux, so much the better."

Goulde says this will impact developers: "If I'm writing .NET applications, I might like to -- or be required to -- store stuff on a Sun server," he says. "Maybe it's the standard in the corporate data center; maybe it's for security reasons."

Where does all this leave Samba, the open source implementation of CIFS, currently supported by Solaris and commonly shipped with Linux?

"Samba is a reverse engineering of the Microsoft SMB protocol," Goulde observes. "CIFS is a standard. There are limitations in Samba that don't exist in CIFS, and there are other technological advantages to CIFS -- things like Unicode, Access Control Lists and aggressive caching."

"It's not a question of whether or not Samba is good enough; the question is which solution is right for each customer," Wright says. "Samba is a good, robust solution for environments with multiple Unix variants, and when portability across diverse platforms is important. The trade-off is integrated, native support versus portability."

Sun plans to incorporate CIFS Server in the upcoming "Indiana" release of OpenSolaris, Wright says. Indiana is due in early 2008. Wright provides more details on his blog, which can be found at

About the Author

John K. Waters is a freelance author and journalist based in Silicon Valley. His latest book is The Everything Guide to Social Media. Follow John on Twitter, read his blog on, check out his author page on Amazon, or e-mail him at

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