Introduction to the XrootdFS

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Introduction to the XrootdFS Wei Yang Andy
Hanushevsky
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• What is XroodFS and Why
• Xrootd provides a Posix I/O interface
• open(), close(), read(), write(), etc., in
  addition to the native XTNetFile class
• XrootdFS provides a Posix File System layer
• Mount the Xrootd storage cluster to a desktop
  machine
• Provide a complete view of storage tree, with the
  help of the Composite Name Space
• Base on FUSE, implemented using Xrootd Posix I/O
  library
• Many software assume a Posix File System

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• Composite Name Space
• A Standalone Xrootd instance (CNS) hosting
  shadow of all files in the Xrootd storage
  cluster
• Shadows are empty files, use no space but
  i-nodes
• Directory tree provide a complete view of the
  storage space
• Sync creation and deletion of shadow file and
  real data file
• XrdCns daemon on data servers, forwarding
  create(), closew() and mkdir() to CNS
• Xrootd broadcasting unlink(), rename(), rmdir()
  and truncate() to all data servers and CNS
• Usually run on the Redirector

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XrootdFS
User
Redirector broadcasts unlink(),
rename(), rmdir() and truncate()
XrootdFS
redirector
XrootdFS
XrootdFS
Xrootd
Xrootd (CNS)
XrdCnsd forward create(), closew(), mkdir()
Each Xrootd data server contains part of the
directory tree CNS has a complete directory tree,
with shadow files http//wt2.slac.stanford.edu/xr
ootdfs/xrootdfs.html
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FUSE I/O is Expensive
Xrootd storage cluster
User probram
XrootdFS daemon
User space Kernel space
File system layer
Client host