Consider the Unix i-node which uses 12 direct DBAs, 1 single indirect, 1…
2020
Consider the Unix i-node which uses 12 direct DBAs, 1 single indirect, 1 double indirect, 1 triple indirect. The disk block address requires 32 bits and disk block size is 1 KB. What is the maximum file size?
- A.
32 GB
- B.
64 GB
- C.
16 GB
- D.
8 GB
Attempted by 68 students.
Show answer & explanation
Correct answer: C
Disk Block Size (DBS): 1 KB = 210 bytes
Disk Block Address (DBA) size: 32 bits = 4 bytes
Number of entries per index block (N): DBS / DBA size = 1 KB / 4 bytes = 1024/4 = 256 = 28
Maximum File Size Formula:
Max File Size =(Direct DBAs + 1 x N + 1 x N2 + 1 x N3 x DBS)
The highest-order term (N3) dominant value determines the maximum approximate size:
Max File Size = N3 x DBS = (28)3 x 1 KB} = 224 x 210 bytes = 234 bytes = 16 GB
Thus, the exact maximum size is just slightly over 16 GB. The correct option is C.