HP Compaq Integrated Smart Array Controller - Manual (Page 116)

B-10 Compaq Integrated Smart Array Controller User Guide
Compaq Confidential – Need to Know Required
Writer: CDresden Project: Compaq Integrated Smart Array Controller User Guide Comments:
Part Number: 153236-001 File Name: i-appb Understanding Drive Arrays.doc Last Saved On: 8/27/99 11:35 AM
Performance Enhancement
Drive arrays allow data access performance to be enhanced dramatically over
nonarrayed drives. In addition, the Integrated Smart Array Controller has
several other performance enhancement features that are discussed here.
Distributing Data and Data Striping
Distributing data makes it possible to access data concurrently from multiple
drives in an array. This yields I/O rates many times faster than nonarrayed
drives. Distributing data allows data striping as shown in the following figure.
Data striping is automatically generated on an array controller in order to store
user data. A stripe is a collection of contiguous data that is distributed evenly
across all physical drives in a logical drive. The width of the stripe (the
amount stored on each physical drive) is selected to optimize the performance
of the operating system.
For example, consider an operating system that typically requests data in
32-sector blocks. The Integrated Smart Array Controller distributes the data so
that the first 32 sectors of data are on the first drive in the array. The Integrated
Smart Array Controller continues distributing the next 32 sectors on the
second drive, the next 32 sectors on the third drive, and so on. Evenly
distributed data results in improved performance by allowing data access to all
drives simultaneously.
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Figure B-7. Data striping distributes data across all physical drives