Once you’ve understood what OpenAFS is, you might ask “Why use OpenAFS?” There are several very good reasons to consider OpenAFS.
First, if you need a cross-platform network filesystem, OpenAFS is a solid choice. While CIFS is the natural choice on Windows, and NFS is a natural choice on Unix, OpenAFS gives a hetergeneous choice (and it works on Mac OS X, too).
Setting aside which filesystem is natural for a given platform, though, OpenAFS has a strong advantage with respect to remote access. While it’s common to access systems remotely via a Virtual Private Network (VPN), Secure Shell (SSH), or Remote Desktop, OpenAFS allows the actual files themselves to be shared across a WAN, a dialup link, or a mobile device (and since OpenAFS is cross platform, the issue of which remote sets of remote access software to support is lessened). Having files appear to be local to the device reduces the need for remote access systems and simplifies access. The big win, though, is that OpenAFS’ file caching helps performance and lessens bandwidth requirements.
Another reason to use OpenAFS is if you need your network filesystem to be secure. While both CIFS and NFS have secure versions, in practice, they are often configured to be backwards compatible to a least common denominator and are relatively insecure. Typically, either they trust the client to be secure (NFS), or the backwards compatibility significantly lessens security (CIFS). While for an isolated or trusted network, their security mechanisms may be acceptable, OpenAFS can relied on over an untrusted network. Common practice for allowing CIFS and/or NFS accesses over an untrusted network is to leverage a VPN, which introduces yet another piece of software to manage. On the other hand, OpenAFS ’just works’ over an untrusted network and it makes no assumptions about the trustworthiness of the client.
Business growth often drives opening new offices. Sharing data across those offices can be a challenge, and OpenAFS, because it was designed to be a wide area filesystem, not just a local area filesystem, shines. By creating a global namespace and linking the offices together, all data in all offices can be accessed seamlessly. This can be as simple as two offices, one central with OpenAFS servers and the other remote, with only OpenAFS clients, or it can scale up a step to where each remote office holds file and meta-data servers so that commonly shared local files can be accessed more quickly. It can even scale up globally with a more complex environment. Morgan Stanley’s environment as of Spring 2008 had around 500 servers globally, providing OpenAFS file services to tens of thousands of Unix and Windows clients in approximately 100 offices. No other network filesystem offers such amazing scalability.
Business challenges often mean closing offices, and OpenAFS’ flexibility works well here, too. Since data can be moved while on-line, servers in an office can be migrated to a different location, and OpenAFS clients will automatically get data from the new location, making removal of the infrastructure in an office straightforward.
OpenAFS’s ability to scale down to a single office and up to a complex global environment sets it apart from all other network filesystems. If you need a network filesystem, why not choose OpenAFS? It will let you grow without having to go through a filesystem switch when you find that your current choice limits your ability to accomplish your goals.