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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

Homework 9

Sarah Diesburg

Operating Systems

COP 4610

hierarchical name space

/

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
hierarchical name space1

/

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

hierarchical name space2

/

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

hierarchical name space3

/

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

hierarchical name space4

/

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

hierarchical name space5

/

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

hierarchical name space6
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
how would you design your file system differently
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?
file system components
File System Components
  • Disk layout
  • Naming
  • Protection
  • Reliability
infinite number of cpus
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
infinite memory size
Infinite Memory Size
  • Load (cache) all file to data mappings into memory on boot
  • Memory-map files to disk
infinite disk storage
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
infinite network bandwidth
Infinite Network Bandwidth
  • Automatic remote copy (remote RAID 1?)
  • Store metadata locally (accessed more often), store data remotely (accessed less often)
how would you design a file system
How would you design a file system
  • for only large files?
  • for only small files?
  • if memory capacity == disk capacity
for large files
For large files
  • Multi-level indexed allocation
  • Hash allocation – change to one block won’t affect rest
for small files
For small files
  • Indexed allocation
  • Small segmented allocation
memory capacity disk capacity
Memory capacity = Disk capacity
  • Cache all metadata and files as they are being used