User manual

2 An Introduction to RAID

2.1 RAID Volumes

RAID technology allows one or more disks to be combined into a logical volume which provides greater performance and/or

protection than standard disk drives. These volumes, also known as RAID Groups, appear like regular disk drives to the

operating system and can be partitioned, formatted and used just like any other normal disk. The complexity of the RAID is

hidden within the driver.

There are several different methods of combining disks, each with its own advantages and disadvantages. Each method is

referred to as a RAID “level” such as RAID 1, or RAID 5. The details of each level are summarized below and detailed in the

following sections.

RAID Level Advantages Disadvantages

0 Excellent performance, low cost No data protection

1 Excellent data protection High cost

5 Good data protection, good value Some performance degradation for

writes.

10 High performance, excellent data

protection.

High cost.

Concatenation Good performance, low cost No data protection

JBOD Same as single disk Same as single disk

2.2 Segmenting Disks

For increased versatility, the SATARAID5 software allows individual disks to be divided into smaller segments which can then

be combined into different volumes. As an example, if a user has one set of data that must be protected at all costs, another

set of data which should be protected at reasonable cost and another set that doesn’t need any protection at all, the user can

divide three disks into sections as shown in Figure 1. The yellow regions define the high security volume, the greem section is

the middle security volume and the light blue shows the unprotected area.

Figure 1: Dividing Disks into Members