Question

Explain the double-indirect inode pointer. Be sure to include how many blocks can be accessed with this structure.

Answer 1

The pointers referred to are disk block addresses - each pointer contains the information necessary to identify a block on disk. Since each disk block is at least 512 bytes (sometimes 4096 or 8192 bytes), using 32-bit addresses the disk can address up to 512 * 4 * 10243 = 2 TiB (Tebibytes - more commonly called Terabytes) assuming 1/2 KiB blocks; correspondingly larger sizes as the block size grows (so 32 TiB at 8 KiB block size). For an addressing scheme for larger disks, you would have to move to larger block sizes or larger disk addresses - hence 48-bit or 64-bit addresses might be plausible.