DAFS for NAS
The Direct Attached File System (DAFS) specification provides a method of doing file transfers between devices without operating system intervention and with minimal CPU overhead. As DAFS gels from a newly adopted standard into a series of products, one of the first beneficiaries promises to be NAS.
In essence, DAFS is a stripped-down, speeded-up re-take on NFSv4. It uses NFSv4's semantics, but is optimized for the capabilities of the Virtual Interface (VI) cluster interconnect architecture standard developed by Microsoft, Intel and Compaq. Among other features, VI provides remote direct memory access, which lets a VI device put information directly into an application's buffers. DAFS lets applications make direct connections to storage devices using a standard API and a DAFS-enabled network card. The DAFS philosophy is to eliminate all the buffers, packet acknowledgments and other things that slow down data transfer. One result is that DAFS is designed to work over short distances on high-reliability networks in a trusted environment. Another result is file transfers at speeds that rival SANs.
All this makes the NAS community's eyes light up because it makes DAFS a natural fit for NAS. DAFS promises to provide NAS filers and other devices with a fast, fairly simple, method of moving data to where it is needed. It doesn't hurt that like NAS, DAFS is file oriented.
DAFS is still very new and the
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
This was first published in January 2002