P2P filesystem Sam Prentice & Sudeep Pillai Central Extent - - PowerPoint PPT Presentation

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P2P filesystem Sam Prentice & Sudeep Pillai Central Extent - - PowerPoint PPT Presentation

Feb 01, 2023 6 likes •116 views

P2P filesystem Sam Prentice & Sudeep Pillai Central Extent Server YFS YFS YFS YFS Lock Extent Server Server Distributed Extents YFS YFS YFS YFS Local Extent Local Extent Local Extent Local Extent Light-weight extent

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SLIDE 1

P2P filesystem

Sam Prentice & Sudeep Pillai

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SLIDE 2

YFS YFS YFS YFS Lock Server

Central Extent Server

Extent Server

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SLIDE 3

YFS YFS YFS YFS

Light-weight extent membership service

Lock Server

Distributed Extents

Local Extent Local Extent Local Extent Local Extent

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SLIDE 4

Shared+Exclusive Locking

  • Shared access: Multiple readers
  • acquire_read
  • Exclusive access: Single writer
  • acquire_write
  • Pitfalls
  • Writer Starvation: Lock contention where writer

waits on same lock that several readers request

– Lock granted to either single writer in queue head

OR

– Lock granted to group of readers in queue head

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SLIDE 5

Optimizations

  • Typical lock transition mechanism
  • acquire-revoke-release-retry cycle
  • Lock upgrading/downgrading
  • Upgrading (R->W): Revoke read access for every
  • ther client
  • Downgrading (W->R): Clients with write access

permitted to read until revocation

– Optimize special cases: new read requests not preceded

by write request granted immediately

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SLIDE 6

Distributed Extents

  • Extents reside distributed across clients
  • Freshest extents are directly read by clients

via P2P

  • Avoid flushing data to central extent server
  • Extent ID membership held centrally
  • Latest writer/owner is tracked
  • Peers can request for latest owner for fresh copies
  • Allows distributing of hot-spots in filesystem
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SLIDE 7

Load Balancing

  • Load distributed

evenly across clients

  • Reduced bandwidth

per client compared to central extent server which did the heavy-lifting

P2P Load balancing test with 10 clients

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SLIDE 8

Benchmarking

Centralized Extent Server Distributed Extents

  • Handles well with hot-spots of file-system

usage

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SLIDE 9

Thanks!

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SLIDE 10

Sequential consistency

  • Readers and writers see the most recent

extent copy

  • Modifications only made by exclusive writer
  • Difficulties
  • Ensure extent attribute synchronization
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SLIDE 11

Benchmarking

  • RPC counts

Central P2P test-lab-3-c 1400 400 Central P2P test-lab-3-c

~1600 ms ~1250 ms

  • Timing
  • Bandwidth

Central P2P test-lab-3-c 27.02 MB 14.31 MB