Direct Access File System (DAFS): Duke University Demo Source-release reference implementation of DAFS Broader research goal: Enabling efficient and transparently scalable Internet-based storage and content services Example applications built on TPIE framework –Merge –TerraFlow – GIS DAFS vs. NFS Participants: Jeff Chase, Richard Kisley, Andrew Gallatin, Rajiv Wickremesinghe, Darrell Anderson, Ken Yocum. Collaborators: Margo Seltzer, Norm Hutchinson. Funding provided by Network Appliance and by the National Science Foundation under grant EIA (ESS), with infrastructure support from EIA (RI).

DAFS Demo Testbed DAFS / NFS Client 256MB SDRAM DAFS / NFS Server 512MB SDRAM cLAN GigEther 86 MB/s Testbed allows direct comparison of DAFS and NFS applications

User Space OS Kernel PCI Bus NIC TPIE: One Application–Two File Systems DMA User Applications TPIE Library cLAN VIA Adapter DAFS Client cLAN VIA cLAN VIPL Library cLAN Device Driver DAFS Client Library copyin/out DMA User Applications TPIE Library VFS/VM Buffercache NFS TCP/IP Stack Ethernet Device Driver Alteon Gigabit Ethernet Adapter NFS Client Ethernet

Benefits of DAFS Low I/O overhead –Copy-avoidance with RDMA –Improves application performance up to 2x depending on the I/O demands of the application –Benefits may be much higher since the NFS in our experiments is highly optimized User-level networking –Enabled by the Emulex/Giganet clan VI network –Reduced protocol overhead on the host –Reduced context switching on the host

TPIE Merge Application Key component of external sort algorithm –Basic primitive of many external memory applications Sequential I/O: reads and writes Merge parameters control compute-I/O ratio –Merge order increases complexity of merge computation –Record density (records / MB) increases the number of merge computations that must be done between I/O’s