Implementation and Evaluation of a Multimedia File System

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Implementation and Evaluation of a Multimedia
File System

• T.N.Niranjan
• Tzi-cker Chiueh
• Gerhard A. Schloss
• Department of Computer Science
• State University of New York at Stony Brook
• 1997 IEEE
• Presented by Sharon Shen

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OVERVIEW

• Introduction
• Related Work
• MMFS Design
• Performance Evaluation
• Conclusions and future work

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INTRODUCTION

• Multimedia unique demands in file system
• MMFS extends UFS
• Supports a two dimensional file structure
• Single medium editing
• Multiple-media playback environments
• A fully functional file system based on the VFS

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INTRODUCTION

• Classification of multimedia applications
• Playback oriented
• Concerned with real-time constraints and
  synchronized retrieval
• Development oriented
• Require system support to manipulate compositions

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INTRODUCTION

• MMFS offers a set of functionalities for
  multimedia support
• Synchronized multi-stream retrieval
• Editing support
• Caching and prefetching optimizations
• Real-time disk scheduling

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RELATED WORK

• UCSD multimedia server
• CMFS
• Mitra SBVS
• IBM Tiger Shark
• YARTOS

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RELATED WORK

• Tactus toolkit Acme I/O Server
• Audition audio system
• MMFS could not provide real-time guarantees to
  multimedia playback
• Vagaries of the FreeBSD process scheduler
• Lack of admission control
• Re-implementation on Unix OS augmented with
  real-time support make this feature feasible

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MMFS DESIGN

• Extends the UNIX file structure
• A single-medium strand abstraction
• An MM file construct tie multiple strands
• An MM file is associated with unique mnode
• Mnode contains the metadata of the MM file
• Mutimedia-specific metadata of each strand
• (recording rate,logical block size, the size of
  the application data unit)

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MMFS DESIGN

• Reduction of the impedance mismatch between
  the multimedia applications and the file system
• Used for low-level optimization
• MMFS API
• Add an extra argument mminfo
• Add/Remove strands from an MM file
• Insert/Delete data from strands

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MMFS DESIGN
Prefetching

• Unix file system
• Sequential reads are common
• Each open file is associated with a read-ahead
  length(v_ralen) in its vnode
• Not sequential read?prefetching is avoid and
  exponential back-off of v_ralen is initiated

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MMFS DESIGN
Prefetching

• Playback of a video in reverse
• UFS identify non-sequential read?reduce the
  degree of prefetching
• MMFS allows the application to advise the file
  system reverse the direction
• Setting mminfo-gtdirection to REVERSE
• Passing mminfo as an argument to mmread

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MMFS DESIGN
Prefetching

• Playback of a video in fast-forward
• UFS Prefetching ( issue read-aheads for
  unnecessary blocks)

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MMFS DESIGN
Prefetching

• Playback of a video in fast-forward
• MMFS perform intelligent prefetching
• Applications communicate MMFS
• Setting the fields in mminfo (retrieval
  rate,direction,whether frames skip)
• Degree of prefetching is maintained at a high
  level
• Note It does not work for compressed data
• streams

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MMFS DESIGN
Prioritized real-time disk scheduling

• UFS using SCAN
• Order the request by the position of the
  requested physical block on the disk surface
• nonRT operations queued with RT multimedia
  operations

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MMFS DESIGN
Prioritized real-time disk scheduling

• MMFS using priority
• Higher priority RT request, lower priority
  nonRT request
• Non-preemptive Scheduling
• Assign a deadline with each mmread request
• Use Earliest Deadline First scheduling for RT use
  SCAN for nonRT request
• Starvation possible for nonRT

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MMFS DESIGN
Support for synchronization

• Quality of synchronization measured by the amount
  of skew
• MMFS considers each strand as a temporally
  continuous stream of data
• Specify mmbind, synchronized retrieval the given
  strands
• MMFS constructs a round-robin retrieval schedule
  for these strands
• An mmunbind call issued when synchronization is
  no longer required

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MMFS DESIGN
Support for Editing

• UFS use write, truncate system calls for small
  size file
• Multimedia editing large uncompressed files
• MMFS provide mminsert and mmdelete

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MMFS PERFORMANCE EVALUATION
Evaluation Environment

• Multimedia data residing in local IDE disk of
  Pentium-90
• Compare MMFS with UFS of FreeBSD 2.0.5

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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization

• Parameters of experiment

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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization

• Response Time time taken between the issuance of
  read request and the reception of the request
  data
• Delayed If the response time is more than 130
  of the frame duration
• Performance metric fraction of delayed frames

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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization

• Reverse playback

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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization

• Fast forward playback

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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization

• Fast reverse playback

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MMFS PERFORMANCE EVALUATION
Impact of prioritized RT disk scheduling

• Effect of nonRT load

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MMFS PERFORMANCE EVALUATION
Impact of prioritized RT disk scheduling

• Effect of RT load

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MMFS PERFORMANCE EVALUATION
Impact of synchronization support

• Multi-Strand Playback

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MMFS PERFORMANCE EVALUATION
Impact of synchronization support
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CONCLUSIONS FUTURE WORK

• UFS assumptions and design decision are not
  appropriate for multimedia
• MMFS prefetching optimization allow applications
  to playback streams at higher access rate and
  different directions
• MMFS disk scheduler maintains the performance of
  the multimedia application when RT and nonRT
  application are simultaneously active

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CONCLUSIONS FUTURE WORK

• MMFS editing primitives offer an excellent
  response to development applications
• MMFS bridges the gap between generic file systems
  and special-purpose servers
• MMFS provides real-time process scheduling to
  meet QoS requirements

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CONCLUSIONS FUTURE WORK

• The idea embedded in MMFS are widely applicable
  to any general-purpose file system
• Many enhancements to the current implementation
  are possible
• The impact of variable-rate compression on MMFS
  optimizations have to be studied
• The feasibility of extending MMFS to a
  distributed environment deserves investigation

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REFERENCES

• Niranjan, T. N. File System Support for
  multimedia applications. PhD thesis, SUNY at
  Stony Brook, December 1996. At http//www.cs.sunys
  b.edu/niranjan/thesis.ps.gz
• Niranjan, T. N. and Schloss. F. State-based
  buffer-cache design for a multimedia file system.
  In Proc. Of the Sixth Int. Workshop in Network
  and Operating System Support for Digital Audio
  and Video(NOSSDAV), April 1996

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• Q A
• Thank You !