HP ProLiant 4500 Disk Subsystem Performance and Scalability - Page 6

Initial, Configuration

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ECG025.0997 WHITE PAPER (cont.) ... One method to decrease seek time is to distribute data across multiple drives. For instance, the initial configuration in Figure 1 shows a single disk containing data. The new configuration reflects the data being striped across multiple disks. This method reduces seek time because the data is spread evenly across two drives instead of one, thus the disk head has less distance to travel. Furthermore, this method increases data capacity because the two disks provide twice the space to store data. Initial Configuration Seek Time Data New Configuration Data Data Seek Time Unused space Seek Time Unused space Figure 1: Average Seek Time and Capacity You can use this same concept and apply it to many different configurations. For example, if you currently have a two-disk configuration but you want to decrease the average seek time yet increase the disk capacity, you can configure a striped set of disks using four disks instead of two. This concept applies to any configuration (odd or even number of disks) as long as you are adding more drives to your stripe set. 6

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One method to decrease seek time is to distribute data across multiple drives.
For
instance, the initial configuration in Figure 1 shows a single disk containing data.
The
new configuration reflects the data being striped across multiple disks.
This method
reduces seek time because the data is spread evenly across two drives instead of one,
thus the disk head has less distance to travel.
Furthermore, this method increases data
capacity because the two disks provide twice the space to store data.
Data
Seek Time
Initial
Configuration
New
Configuration
Unused space
Unused space
Data
Seek Time
Seek Time
Unused space
Data
Figure 1: Average Seek Time and Capacity
You can use this same concept and apply it to many different configurations.
For
example, if you currently have a two-disk configuration but you want to decrease the
average seek time yet increase the disk capacity, you can configure a striped set of disks
using four disks instead of two.
This concept applies to any configuration (odd or even
number of disks) as long as you are adding more drives to your stripe set.