Compaq 108164-003 - ProLiant - 800 White Paper page 6

ECG025.0997
W P
HITE APER
(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
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
New
. .
. .
Configuration
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
. .
Seek Time
. .
. .
. .
. .
. .
. .
. .
. .
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
Seek Time
Data
Seek Time
Unused space
Data
Data
Unused space Unused space