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Homework 9

Homework 9. Sarah Diesburg Operating Systems COP 4610. /. Hierarchical Name Space. To access the data content of /pets/cat.jpg The system needs to perform the following disk I/Os 1. Read in the file header for the root directory ‘/’ Stored at a fixed location on disk. /.

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Homework 9

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  1. Homework 9 Sarah Diesburg Operating Systems COP 4610

  2. / Hierarchical Name Space • To access the data content of /pets/cat.jpg • The system needs to perform the following disk I/Os 1. Read in the file header for the root directory ‘/’ • Stored at a fixed location on disk

  3. / Hierarchical Name Space • To access the data content of /pets/cat.jpg • The system needs to perform the following disk I/Os 2. Read the first data block for the root directory • Lookup the directory entry for pets pets

  4. / Hierarchical Name Space • To access the data content of /pets/cat.jpg • The system needs to perform the following disk I/Os 3. Read the file header for pets pets pets

  5. / Hierarchical Name Space • To access the data content of /pets/cat.jpg • The system needs to perform the following disk I/Os 4. Read the first data block for the pet directory • Lookup the directory entry for cat.jpg pets pets cat

  6. / Hierarchical Name Space • To access the data content of /pets/cat.jpg • The system needs to perform the following disk I/Os 5. Read the file header for cat.jpg pets cat pets cat

  7. / Hierarchical Name Space • To access the data content of /pets/cat.jpg • The system needs to perform the following disk I/Os 6. Read the data block for cat.jpg pets cat pets cat

  8. Hierarchical Name Space • So how many disk I/Os do we need to resolve the path? • Depends what resolving means • 5 to resolve the path (everything but reading the file) • 6 if resolving includes reading the first file data block

  9. How would you design your file system differently? • If you have infinite number of CPUs? • If you have infinite memory size? • If you have infinite disk storage? • If you have infinite network bandwidth?

  10. File System Components • Disk layout • Naming • Protection • Reliability

  11. Infinite Number of CPUs • Some of you forgot to think about disk seek and data transfer times • These are separate from computational power • Use naming schemes that take a lot of computational power • E.g., relational, contextual, content-based • Hash data block locations • Maybe encryption for extra security

  12. Infinite Memory Size • Load (cache) all file to data mappings into memory on boot • Memory-map files to disk

  13. Infinite Disk Storage • Make extra copies for reliability • Make extra copies for speed • Contiguous or segment-based allocation • No longer need to worry about external fragmentation

  14. Infinite Network Bandwidth • Automatic remote copy (remote RAID 1?) • Store metadata locally (accessed more often), store data remotely (accessed less often)

  15. How would you design a file system • for only large files? • for only small files? • if memory capacity == disk capacity

  16. For large files • Multi-level indexed allocation • Hash allocation – change to one block won’t affect rest

  17. For small files • Indexed allocation • Small segmented allocation

  18. Memory capacity = Disk capacity • Cache all metadata and files as they are being used

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