GU1: 10. Disk Performance

Disk Performance: What are the two ways of assessing a hard disks performance?

Seek time

Transfer rate

Disk Performance: What is "seek time"?

Seek time, or “response time” is how long it takes for the data to be found on the disk (prior to transfer). Access time is measured in nanoseconds

Disk Performance: What affects "seek time"?

The disks moving parts (read/write heads, platter rotation).

Disk Performance: What is the "transfer rate" in relation to disk performance?

The transfer rate, also known as “throughput”, is the speed at which a hard drive can transfer information. It is measured in MB/s.

Disk Performance: What affects "transfer rate"?

Seek time

RPM of the drive

Disk fragmentation

Data location (outer track vs inner track)

Disk Performance: What is clock speed?

Number of cycles per second (Hz)

Disk Performance: Does higher clock speed always mean better performance?

No — depends on no of cores, size of cache, architecture.

Disk Performance: What is an interrupt?

Signal that pauses CPU to handle an urgent task.

Disk Performance: What happens during an interrupt?

CPU pauses current task

Saves state

Executes interrupt service routine

Returns to task

Disk Performance: What is an interrupt service routine (ISR)?

Code that handles the interrupt. It pauses the current program, deals with the interrupt, then returns the control to the original program.

Disk Performance: Give an example of an interrupt.

Keyboard input

Mouse click

Signal from i/o

Network activity

Disk Performance: What are 6 factors that affect CPU performance?

Clock speed

Number of cores

Cache size

Bus width

RAM amount/speed

Architecture