GATE CSE 2003 | Question: 25, ISRO2009-12

Question

Using a larger block size in a fixed block size file system leads to

• A. better disk throughput but poorer disk space utilization
• B. better disk throughput and better disk space utilization
• C. poorer disk throughput but better disk space utilization
• D. poorer disk throughput and poorer disk space utilization

Answer 1

Answer is (A). Larger block size means less number of blocks to fetch and hence better throughput. But larger block size also means space is wasted when only small size is required.

Comments

But it also adds to internal fragmentation if file size not equal to block size as mentioned by arjun sir.

---

If the block size is large then we have to access fewer blocks as more data will be present in each block .So less seek time and rotational delay

will be required .So the data that can be read from or written into the disk per unit time will increase .

Thus disk throughput will increase.

 

 

---

@Arjun Sir, how can you always guarantee that disk throughput will be higher? I mean if the size is so big that some blocks span across cylinders then additional seek times also have to be encountered right?

Answer 2

ans is a 

If block size is large then seek time is less (fewer blocks to seek) and disk performance is improved, but remember larger block size also causes waste of disk space.

Answer 3

If the block size is large then seek time is less (fewer blocks to seek) and disk performance is improved,
but larger block size also causes waste of disk space.

So option a is correct.

Answer 4

D.

Using larger block size makes disk utilization poorer as more space would be wasted for small data in a block. It may make throughput poor as the number of blocks would decrease.