GATE IT 2004 | Question: 67

Question

In a particular Unix OS, each data block is of size $1024$ bytes, each node has $10$ direct data block addresses and three additional addresses: one for single indirect block, one for double indirect block and one for triple indirect block. Also, each block can contain addresses for $128$ blocks. Which one of the following is approximately the maximum size of a file in the file system?

• A. $512$ MB
• B. $2$ GB
• C. $8$ GB
• D. $16$ GB

Comments

$Ans:B$

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1.Maximum file size

2.Total size of file system

3.maximum possible file size

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$\left(2^{7}\right)^3 \times 2^{10}=2^{31}=2GB$

Answer 1

Its 2GB

Comments

pls somebody make it understand to mee pls pls explain
a big thanks in advance

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They are asking size of the file. That means all we need to calculate is number of blocks*size of block to know the size of file. since files are being stored as blocks. 

 To calculate total number of blocks 

Block size =1024 bytes

1)Directly given blocks   10*1024 bytes

2)single indirect block    1*128*1024 bytes  (since 1 block is pointing to a block which has 128 address of 128 blocks each of size 1024. since it is given each block will have address of 128 other blocks

3)double, triple indirects with same logics 

totally adding them gives total block sizes

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now clear..!! :)

Answer 2

Block Size = 2^10B

No. of block pointer in one block = 2^7

Total no. of block pointers = 10+2^7+2^7*2^7+2^7*2^7*2^7

                            = 10+2^7+2^14+2^21

Max file Size = (10+2^7+2^14+2^21)*1KB

              = 2113674KB

              = 2.01575660706 MB (option B)