Implementation and Evaluation of a Multimedia File SystemOVERVIEWINTRODUCTIONSlide 4Slide 5RELATED WORKSlide 7MMFS DESIGNSlide 9MMFS DESIGN PrefetchingSlide 11Slide 12Slide 13MMFS DESIGN Prioritized real-time disk schedulingSlide 15MMFS DESIGN Support for synchronizationMMFS DESIGN Support for EditingMMFS PERFORMANCE EVALUATION Evaluation EnvironmentMMFS PERFORMANCE EVALUATION Impact of prefetching optimizationSlide 20Slide 21Slide 22Slide 23MMFS PERFORMANCE EVALUATION Impact of prioritized RT disk schedulingSlide 25MMFS PERFORMANCE EVALUATION Impact of synchronization supportSlide 27CONCLUSIONS & FUTURE WORKSlide 29Slide 30REFERENCESImplementation and Evaluation of a Multimedia File SystemT.N.NiranjanTzi-cker ChiuehGerhard A. SchlossDepartment of Computer ScienceState University of New York at Stony Brook1997 IEEEPresented by Sharon ShenOVERVIEWIntroductionRelated WorkMMFS DesignPerformance EvaluationConclusions and future workINTRODUCTIONMultimedia unique demands in file systemMMFS extends UFSSupports a two dimensional file structure–Single medium editing–Multiple-media playback environmentsA fully functional file system based on the VFSINTRODUCTIONClassification of multimedia applications–Playback orientedConcerned with real-time constraints and synchronized retrieval –Development orientedRequire system support to manipulate compositionsINTRODUCTIONMMFS offers a set of functionalities for multimedia support–Synchronized multi-stream retrieval–Editing support–Caching and prefetching optimizations–Real-time disk schedulingRELATED WORKUCSD multimedia serverCMFSMitra & SBVSIBM Tiger SharkYARTOSRELATED WORKTactus toolkit & Acme I/O ServerAudition audio systemMMFS 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 feasibleMMFS DESIGNExtends the UNIX file structure–A single-medium strand abstraction–An MM file construct: tie multiple strands–An MM file is associated with unique mnodeMnode contains the metadata of the MM fileMutimedia-specific metadata of each strand(recording rate,logical block size, the size of the application data unit)MMFS DESIGNReduction of the “impedance mismatch” between the multimedia applications and the file system–Used for low-level optimization–MMFS APIAdd an extra argument mminfo Add/Remove strands from an MM fileInsert/Delete data from strandsMMFS DESIGN PrefetchingUnix file system–Sequential reads are common–Each open file is associated with a read-ahead length(v_ralen) in its vnode–Not sequential readprefetching is avoid and exponential back-off of v_ralen is initiatedMMFS DESIGN PrefetchingPlayback of a video in reverse–UFS identify non-sequential readreduce the degree of prefetching–MMFS allows the application to advise the file system reverse the directionSetting mminfo->direction to REVERSEPassing mminfo as an argument to mmreadMMFS DESIGN PrefetchingPlayback of a video in fast-forward–UFS Prefetching ( issue read-aheads for unnecessary blocks)MMFS DESIGN PrefetchingPlayback of a video in fast-forward–MMFS perform intelligent prefetchingApplications communicate MMFSSetting the fields in mminfo (retrieval rate,direction,whether frames skip)Degree of prefetching is maintained at a high levelNote: It does not work for compressed data streamsMMFS DESIGN Prioritized real-time disk schedulingUFS using SCAN–Order the request by the position of the requested physical block on the disk surface–nonRT operations queued with RT multimedia operationsMMFS DESIGN Prioritized real-time disk schedulingMMFS 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 nonRTMMFS DESIGN Support for synchronizationQuality of synchronization measured by the amount of skewMMFS considers each strand as a temporally continuous stream of dataSpecify mmbind, synchronized retrieval the given strandsMMFS constructs a round-robin retrieval schedule for these strandsAn mmunbind call issued when synchronization is no longer requiredMMFS DESIGN Support for EditingUFS use write, truncate system calls for small size fileMultimedia editing large uncompressed filesMMFS provide mminsert and mmdeleteMMFS PERFORMANCE EVALUATION Evaluation EnvironmentMultimedia data residing in local IDE disk of Pentium-90Compare MMFS with UFS of FreeBSD 2.0.5MMFS PERFORMANCE EVALUATION Impact of prefetching optimizationParameters of experimentMMFS PERFORMANCE EVALUATION Impact of prefetching optimizationResponse Time: time taken between the issuance of read request and the reception of the request dataDelayed: If the response time is more than 130% of the frame durationPerformance metric: fraction of delayed framesMMFS PERFORMANCE EVALUATION Impact of prefetching optimizationReverse playbackMMFS PERFORMANCE EVALUATION Impact of prefetching optimizationFast forward playbackMMFS PERFORMANCE EVALUATION Impact of prefetching optimizationFast reverse playbackMMFS PERFORMANCE EVALUATION Impact of prioritized RT disk schedulingEffect of nonRT loadMMFS PERFORMANCE EVALUATION Impact of prioritized RT disk schedulingEffect of RT loadMMFS PERFORMANCE EVALUATION Impact of synchronization supportMulti-Strand PlaybackMMFS PERFORMANCE EVALUATION Impact of synchronization supportCONCLUSIONS & FUTURE WORKUFS assumptions and design decision are not appropriate for multimediaMMFS prefetching optimization allow applications to playback streams at higher access rate and different directionsMMFS disk scheduler maintains the performance of the multimedia application when RT and nonRT application are simultaneously activeCONCLUSIONS & FUTURE WORKMMFS editing primitives offer an excellent response to development applicationsMMFS bridges the gap between generic file systems and special-purpose serversMMFS
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