Disk structure and access time in DBMS Theory - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are the main components of a disk structure?

A disk structure mainly consists of platters, tracks, sectors, and cylinders. Platters are circular disks coated with magnetic material. Tracks are concentric circles on a platter. Sectors are subdivisions of tracks, and cylinders are sets of tracks aligned vertically across platters.

beginner

Define seek time in the context of disk access.

Seek time is the time taken by the disk's read/write head to move to the track where the data is stored. It is a major factor in the total time to access data on a disk.

beginner

What is rotational latency and how does it affect disk access time?

Rotational latency is the delay waiting for the disk to rotate the correct sector under the read/write head. It depends on the disk's rotation speed and adds to the total access time.

beginner

Explain transfer time in disk operations.

Transfer time is the time taken to actually read or write the data once the read/write head is positioned correctly. It depends on the amount of data and the disk's data transfer rate.

intermediate

How is total disk access time calculated?

Total disk access time is the sum of seek time, rotational latency, and transfer time. It represents the complete time to read or write data on a disk.

Which part of the disk structure is a circular path on a platter?

A Track

B Sector

C Cylinder

D Cluster

A track is a circular path on the surface of a disk platter where data is recorded.

What does seek time measure?

A Time to format the disk

B Time to rotate the disk to the correct sector

C Time to transfer data

D Time to move the head to the correct track

Seek time is the time taken for the read/write head to move to the track containing the data.

Rotational latency depends on:

A Disk rotation speed

B Head movement speed

C Data transfer rate

D File size

Rotational latency is the delay waiting for the disk to rotate the correct sector under the head, so it depends on rotation speed.

Which of these is NOT part of total disk access time?

A Transfer time

B Rotational latency

C File compression time

D Seek time

File compression time is unrelated to disk access time.

What is a cylinder in disk structure?

A A single sector on a track

B A set of tracks aligned vertically across platters

C The outermost track on a platter

D The read/write head

A cylinder is a group of tracks located at the same position on multiple platters.

Describe the components of disk structure and their roles in storing data.

Think about how data is arranged physically on the disk.

Explain the factors that contribute to disk access time and why each is important.

Consider the steps from moving the head to reading data.