Access time – the time it takes from when a read or write request is issued to when data transfer begins. Consists of: Seek time – time it takes to reposition the arm over the correct track. Question 1: Average seek time is 1/2 the worst case seek time. Explain. Would be 1/3 if all tracks had the same number of sectors, and we ignore the time to start and stop arm movement 4 to 10 milliseconds on typical disks Rotational latency – time it takes for the sector to be accessed to appear under the head. Question 2: Average latency is 1/2 of the worst case latency. Explain. 4 to 11 milliseconds on typical disks (5400 to 15000 r.p.m.) Data-transfer rate – the rate at which data can be retrieved from or stored to the disk. Question 3: 25 to 100 MB per second max rate, lower for inner tracks. Why? Multiple disks may share a controller, so rate that controller can handle is also important
Access time – the time it takes from when a read or write request is issued to when data transfer begins. Consists of: Seek time – time it takes to reposition the arm over the correct track. Question 1: Average seek time is 1/2 the worst case seek time. Explain. Would be 1/3 if all tracks had the same number of sectors, and we ignore the time to start and stop arm movement 4 to 10 milliseconds on typical disks Rotational latency – time it takes for the sector to be accessed to appear under the head. Question 2: Average latency is 1/2 of the worst case latency. Explain. 4 to 11 milliseconds on typical disks (5400 to 15000 r.p.m.) Data-transfer rate – the rate at which data can be retrieved from or stored to the disk. Question 3: 25 to 100 MB per second max rate, lower for inner tracks. Why? Multiple disks may share a controller, so rate that controller can handle is also important
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
Related questions
Question
Access time – the time it takes from when a read or write
request is issued to when data transfer begins.
Consists of:
Seek time – time it takes to reposition the arm over the
correct track.
Question 1: Average
seek time is 1/2 the worst case seek time. Explain.
Would be 1/3 if all tracks had the same number of sectors,
and we ignore the time to start and stop arm movement
4 to 10 milliseconds on typical disks
Rotational latency – time it takes for the sector to be
accessed to appear under the head.
Question 2: Average
latency is 1/2 of the worst case latency. Explain.
4 to 11 milliseconds on typical disks (5400 to 15000 r.p.m.)
Data-transfer rate – the rate at which data can be retrieved
from or stored to the disk.
Question 3: 25 to 100
MB per second max rate, lower for inner tracks. Why?
Multiple disks may share a controller, so rate that
controller can handle is also important
request is issued to when data transfer begins.
Consists of:
Seek time – time it takes to reposition the arm over the
correct track.
Question 1: Average
seek time is 1/2 the worst case seek time. Explain.
Would be 1/3 if all tracks had the same number of sectors,
and we ignore the time to start and stop arm movement
4 to 10 milliseconds on typical disks
Rotational latency – time it takes for the sector to be
accessed to appear under the head.
Question 2: Average
latency is 1/2 of the worst case latency. Explain.
4 to 11 milliseconds on typical disks (5400 to 15000 r.p.m.)
Data-transfer rate – the rate at which data can be retrieved
from or stored to the disk.
Question 3: 25 to 100
MB per second max rate, lower for inner tracks. Why?
Multiple disks may share a controller, so rate that
controller can handle is also important
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