Where’s the data? Dealing With Latency...

• Hierarchical filesystems may have high latency bursts

  • Mounting a tape file

• Need mechanism to notify client of expected delay

  • Prevents request timeout
  • Prevents retransmission storms
  • Also allows server to degrade gracefully
    • Can delay clients when overloaded

• Defer Request Protocol

  • Certain oofs() requests can tell client of expected delay
    • For example, open()
  • Client waits indicated amount of time and tries again

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