HP A7143A RAID160 SA Controller Support Guide, February 2007

RAID Technology Overview

Smart Array Controller Supported RAID Configurations

Chapter 1

Figure 1-5 Disk Drive Mirroring of P1 onto P2 (RAID 1)

The advantages of RAID 1 are as follows:

• No data loss or interruption of service if a disk fails.

• Fast read performance — data is available from either disk.

The disadvantages of RAID 1 are as follows:

• High cost — 50% of disk space is allocated for data protection, so only 50% of total disk drive capacity is

usable for data storage.

RAID 1+0—Disk Drive Mirroring and Striping

RAID 1+0 requires an array with four or more physical disks. The disks are mirrored in pairs and data blocks

are striped across the mirrored pairs.

Figure 1-6 Mirroring and Striping (RAID 1+0)

In each mirrored pair, the physical disk that is not busy answering other requests answers any read request

sent to the array; this behavior is called load balancing. If a physical disk fails, the remaining disk in the

mirrored pair can still provide all the necessary data. Several disks in the array can fail without incurring

data loss, as long as no two failed disks belong to the same mirrored pair.

P1 P2