Unix INODE

Question

Q.1) Consider the Unix inode with 12 Direct Disk Block Addresses(DBA), 1 single indirect DBA, 1 Doubly Indirect DBA and 1 triple indirect DBA. The DBA requires 32 bits and the Disk block size is 1KB. Then what is the maximum file size possible?

Vs

Q.2) A file system with 300 GByte disk uses a file descriptor with 8 direct block addresses, 1 indirect block address and 1 doubly indirect block address. The size of each disk block is 128 KBytes and the size of each disk block address is 8 Bytes. What is the maximum possible file size in this file system?

Vs

What is the Total Size of the File System for both cases?

Comments

Do we need to add all pointers for maximum possible file size in the file system?

or we have to calculate for last indirect or direct blocks..{for eg here in ques 1. we need to calculate maximum file size for triple indirect block addresses as ( 256)³ *1 KB = 16 GB }?

each file has one inode. that means one file can be stored by using direct DBA's or single indirect DBA's or double indirect DBA's or triple indirect DBA's or so on. Isn't like this???

Answer 1

Q1) DBA requires $32$ bits

So, number of address in one block $= \dfrac{2^{10}}{2^2}=2^8$

Maximum possible file size $= \left( 12 + 256 + 256^2 + 256^3 \right) \times 1 \mathrm{ KB} = 16.0627 \mathrm{ GB}$

Q2) Number of address in one block = {2¹⁷} / {2³}=2¹⁴=16384

Max possible file size = ( 8 + 16384 +16384² ) * 128  KB =  268451848 * 128 KB 

Comments

but the disk  can have multiple file systems..

---

For q2) Max possible size of file system  (8 byte address = 64 bit)

But for q2, its explicitly given as 300GB. So 300GB is the final answer, right? Since 300GB < $2^{81}$ B

---

Do anyone know good text content for file system in os Gate syllabus?