Page History

• xrootd
  • Requires more bookkeeping because it has no "ls".
  • I don't trust it - I'm aware that it's not intended to be It's not a drop-in replacement for a disk-based traditional filesystem, and I'm still trying to understand and internalize how it differs from onerequires rethinking assumptions.
  • Could stage input or output files in parallel.
• Combine steps
  • Reduces ability to roll back errors.
  • Increases latency.
• Varying crumb size
  • Makes lots of small crumbs, so digi files get read many times.
• Varying chunk size
  • Lots of small chunks mean more jobs are reading in parallel at the start of processing, but it does not increase the amount of data that's read.
  • If there are more chunks than available cores, that automatically throttles I/O somewhat.

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• PROOF
  • Seems deeply tied to xroot - needs xrootd to run on the batch host? 

• Event collections
  • during processing
    • avoid crumb-to-chunk merges
    • do SVAC at crumb level
  • long-term
    • potentially don't need to merge anything, just store chunk- and crumb-level files 

Using AFS without staging seems very promising to me, I intend to try that first.

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