The document discusses multimedia file systems. It covers multimedia file system paradigms like pull and push servers. It also discusses file placement, caching, and disk scheduling for multimedia. Specifically, it examines strategies for placing files on single and multiple disks, block and file caching, and static and dynamic disk scheduling algorithms.

1. Lecture 2
Multimedia File System
2.1. Multimedia file system paradigms
2.2. File placement
2.3. Caching
2.4. Disk scheduling for multimedia
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2. Multimedia File System Paradigms
Pull and Push Servers
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3. VCR Control Functions
• Rewind is simple
– set next frame to zero
• Fast forward/backward are trickier
– compression makes rapid motion complicated
– special file containg e.g. every 10th frame
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4. Near Video on Demand
New streamhttp://fasilkom.narotama.ac.id/ intervals
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starting at regular
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5. Near Video on Demand with VCR Functions
Buffering for Rewind
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6. File Placement
Frame 1 Frame 2 Frame 3
Audio Text
Frame Frame
Placing a File on a Single Disk
• Interleaving
– Video, audio, text in single contiguous file per movie
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7. Two Alternative File Organization Strategies (1)
• Noncontiguous Movie Storage
(a) small disk blocks
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(b) large disk blocks 7

8. Two Alternative File Organization Strategies (2)
Trade-offs between small, large blocks
1. Frame index
- heavier RAM usage during movie play
- little disk wastage
• Block index (no splitting frames over blocks)
- low RAM usage
- major disk wastage
• Block index (splitting frames over blocks allowed)
- low RAM usage
- no disk wastage
- extra seeks
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9. Placing Files for Near Video on Demand
Optimal frame placement for near video on demand
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10. Placing Multiple files on a Single Disk (1)
• Zipf's law for N=20
• Squares for 20 largest cities in US
– sorted on rank order
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11. Placing Multiple files on a Single Disk (2)
• Organ-pipe distribution of files on server
– most popular movie in middle of disk
Sistem– next most popular either on either side, etc.
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12. Placing Files on Multiple Disks
Organize multimedia files on multiple disks
(a) No striping
(b) Same striping pattern for all files
(c) Staggered striping
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(d) Random striping 12

13. Caching
Block Caching
(a) Two users, same movie 10 sec out of sync
(b) Merging two streams into one
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14. File Caching
• Most movies stored on DVD or tape
– copy to disk when needed
– results in large startup time
– keep most popular movies on disk
• Can keep first few min. of all movies on disk
– start movie from this while remainder is fetched
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15. Disk Scheduling for Multimedia
Stream
Order in which disk requests are processed
Static Disk Scheduling
• In one round, each movie asks for one frame
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16. Dynamic Disk Scheduling
• Scan-EDF algorithm
– uses deadlines & cylinder numbers for scheduling
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17. Question/Discussion
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