DAFS spec awaits IETF green light


The Direct Access File System (DAFS) protocol is one step closer to becoming a standard, but it must overcome a few hurdles before gaining industry acceptance, say analysts.

In late August, the DAFS Collaborative sent version 1.0 of the DAFS spec to the Internet Engineering Task Force (IETF), where it will undergo review as a potential industry standard. This month, the collaborative-which successfully completed its primary goal of developing a specification and submitting it to a standards body-will revamp itself as a Storage Networking Industry Association (SNIA) group called the DAFS Implementers' Forum. The group will be tasked with identifying and encouraging reference implementations of DAFS products.

DAFS is a file-access protocol based on NFS version 4. The protocol is designed specifically for high-performance data-center file sharing. It uses a memory-to-memory I/O architecture and runs on Fibre Channel, Gigabit Ether net, and Infini Band. Basically, DAFS provides a new way for high-performance and cluster applications to access file storage.

"NFS has essentially been the same for 20 years, and DAFS is the first potential new file system architecture-or shared file system architecture," says Steve Duplessie, senior analyst at the Enterprise Storage Group consulting firm.

Figure 1: By using remote memory addressing capabilities of transports such as the virtual interface (VI) architecture and InfiniBand, an application using the DAFS API can read a file without requiring any copies on the client side.
Click here to enlarge image

But while DAFS potentially offers significant advantages for data centers, there are a few hurdles that must be cleared. For example, some DAFS implementations will require application rewrites to get the most out of the technology, according to Duplessie. But the other, more challenging, hurdle is strictly political.

"If DAFS becomes widespread, it will enable a lot of smaller companies to step into the big leagues," explains Duplessie. "It enables super high performance, which has traditionally been the domain of only the biggest vendors."

While the DAFS Implementers' Forum is sponsored by Network Appliance, Intel, and Veritas, at least one key player is missing: EMC. Duplessie believes some companies will not support DAFS in order to protect their market share.

However, the former DAFS Collaborative included 80 member companies that collectively created the DAFS protocol specification in one year. DAFS Implementers' Forum co-chair David Dale, of Network Appliance, is optimistic that more and more storage vendors will join the forum's roster.

Figure 2: DAFS enables applications to access network interface hardware without OS intervention.
Click here to enlarge image

"I'd be surprised if companies with broad storage visions that encompass network-attached storage or next-generation transports don't sign up for it eventually," says Dale.

Meanwhile, the DAFS group is staying on course. Although it is uncertain how long the standards approval process will take, Dale expects initial DAFS products to ship early next year, and by mid-year, DAFS may be running on multiple platforms.

"I think things like InfiniBand will change the way you view I/O over time," says Dale. "A native file-access protocol for InfiniBand that allows you to plug an easy-to-use NAS device into an InfiniBand switch would be a killer application," he adds.

DAFS group revamps

This month, the Direct Access File System (DAFS) Collaborative exercised its "sunset clause" and transitioned into a new group-the DAFS Implementers' Forum-under the wings of the Storage Networking Industry Association (SNIA).

The forum will focus on educating vendors and end users, engaging independent software vendors and users on requirements for integrating DAFS with applications, and identifying and encouraging open source reference implementations of DAFS. In addition, the forum will work to "foster a collaborative ecosystem of vendors around the delivery of DAFS storage networking solutions," says DAFS Implementers' Forum co-chair David Dale of Network Appliance. (The other forum co-chair is Intel's Jim Pappas.)

Some former DAFS Collaborative members will continue refining the specification as part of a working group chartered by the Internet Engineering Task Force, the standards body currently reviewing the DAFS spec. Other companies will work on completing the DAFS API as part of a DAFS API Working Group, which the forum will create to complete the API.

This article was originally published on October 01, 2001