Lecture 22-CSCIU511-Jahangir Majumder-Spring 2025

These flashcards cover key concepts related to File Systems and Disk Scheduling as presented in the CSCI U511 01 Operating Systems lecture.

What is the primary focus of Lecture 22 in CSCI U511 01 Operating Systems?

Discussion on File System and Disk Scheduling.

What is one of the desirable properties of files in a file system?

Long-term existence; files are stored on durable secondary storage.

Name typical operations that can be performed on files in a file system.

Create, Delete, Open, Close, Read, Write.

What are the storage devices mentioned in the lecture notes?

Magnetic disks and Flash memory.

How is disk performance measured?

Disk Latency = Seek Time + Rotation Time + Transfer Time.

What is Seek Time in the context of disk performance?

The time required to move the disk arm to the required track.

Describe the SCAN disk scheduling algorithm.

Moves the disk arm in one direction, serving all requests, then reverses direction.

What does C-SCAN stand for in disk scheduling?

Circular SCAN; the arm only moves in one direction and returns to the opposite end after serving requests.

What is the advantage of the Shortest Service Time First (SSTF) scheduling?

It selects the disk I/O request that requires the least movement of the disk arm.

How does the R-CSCAN scheduling algorithm differ from CSCAN?

R-CSCAN takes into account that short track switches are less than rotational delay.

What is the typical average seek time on contemporary hard disks?

Under 10ms.

What is the significance of rotational delay in disk performance?

It is the time required for the addressed area of the disk to rotate into position for access.