Difference between Transfer Time and Disk Access Time in Disk Scheduling

1. Transfer Time :
Time required to transfer the required amount of data. It can be calculated by the given formula

Transfer time,
= Data to be transfer / transfer rate 

Data to be transfer is given in the question and transfer rate is sometimes given and sometimes it may not be given.

It can be calculated by the given formula.

Transfer Rate,
= {(Number of heads or number of surfaces in the disk)
     *(capacity of one track or number of sectors in each track)
       *(Number of rotations in each track to reach the required sector)}

2. Data Access Time:
It is the total time required to access the data.It means total time required to read/write the data from the disk.
Following is the formula to calculated the data access time:

Data access time,
= {(Seek time) + (Rotational Latency) + (Data Transfer Time)} 

Note:

• Seek time – The time required by R/W head to move to the desired track from the current position.
• Rotational Latency – Time required by sector to come under R/W head.

Difference between Transfer Time and Disk Access Time in Disk Scheduling :

sr.no.	DATA TRANSFER TIME	DATA ACCESS TIME
1	Time required to transfer the required amount of data.	It is the total time required to access the data.It means total time required to read/write the data from the disk.
2	To calculate data transfer time we require only transfer rate	to calculate data access time we require seek time, rotational latency and data transfer time
3	Thus to calculate data transfer time there is no requirement of data access time	To calculate data access time there is the requirement of data transfer time
4	Transfer time=Data to be transfer/transfer rate	Data access time = {(Seek time) + (Rotational Latency) + (Data Transfer Time)}