Q1. Compare the relative advantages and disadvantages of inodes versus file allocation tables.

• inode - stores metadata about a file including TOC.
• FAT - Global TOC.

inode

+   Direct access for single file as needed

–– Requires disk access to load the inode

++ Fast access for random block

++ Support sparse files (holes in file)

–   inode table size limits number of unique files

–   File size limited by inode TOC size

FAT

++ Cached in memory, fast access

–   Requires linked list traversal (though it's in memory)

+   File size only limited by FAT size

–   FAT size limits number of blocks

Refer to lecture slide 54

inode

+   Direct access for single file as needed

–– Requires disk access to load the inode

++ Fast access for random block

++ Support sparse files (holes in file)

–   inode table size limits number of unique files

–   File size limited by inode TOC size

FAT

++ Cached in memory, fast access

–   Requires linked list traversal (though it's in memory)

+   File size only limited by FAT size

–   FAT size limits number of blocks

Which one supports larger file?

• In a Unix implementation where inode TOC has 13 entries, with 10 direct pointer, 1 single/double/triple indirection pointer each, and every index block contains 128 pointers. Further assume that the block size is 8KB. 
  
   
• File sizes in most of the FAT implementations are limited by other factors. 
  • FAT12 supports up to 32MB volumes.
  • FAT16 supports up to 2GB volumes.
  • FAT32 supports up to 4GB minus 1 byte file size (why?)

Q2. Operation with inode

int fseek(FILE *stream, long int offset, int whence)
/* seek to the position of whence + offset.
whence can be 
SEEK_SET (beginning of file), 
SEEK_CUR (current pos), 
SEEK_END (end of file). */
size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)
/* read nmemb number of elements, each with size `size` */

size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
/* similar to fread */

Bracket means pointer is at that block
but nothing read / written

Q3. More operations...

fwrite(buffer, sizeof(int), 1024, fp);
// sizeof(int) = 4 bytes

fseek(fp, 8897, SEEK_SET);
fwrite(buffer, sizeof(char), 1124, fp);

fseek(fp, 3072, SEEK_SET);
fread(buffer, sizeof(char), 1024, fp);

1 0 1 1 0 0 0 1 0 0 0 0 0 0 0 0 

1 1 1 1 1 1 0 1 0 0 0 0 0 0 0 0 

Buffer contains the data in block 4