Direct Access File System (DAFS): Duke University Demo

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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 bythe
  National Science Foundation under grant
  EIA-9870724 (ESS),with infrastructure support
  from EIA-9972879 (RI).

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DAFS Demo Testbed
DAFS / NFS Client 256MB SDRAM
DAFS / NFS Server 512MB SDRAM
cLAN
86 MB/s
GigEther
Testbed allows direct comparison of DAFSand NFS
applications
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TPIE One ApplicationTwo File Systems
DAFS Client
NFS Client
User Applications
User Applications
TPIE Library
TPIE Library
DAFS Client Library
cLAN VIPL Library
copyin/out
DMA
VFS/VM Buffercache
NFS
TCP/IP Stack
cLAN Device Driver
Ethernet Device Driver
DMA
cLAN VIA Adapter
Alteon Gigabit Ethernet Adapter
cLAN VIA
Ethernet
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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

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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/Os