Rosewill RSV-S8 An Introduction To Raid, Raid Volumes, Segmenting Disks, Raid Level, Advantages

Server RSV-S8 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	CONFIGURED AS	ADVANTAGES	DISADVANTAGES
0	Striped	Excellent performance,	No data protection
		low cost
1	Mirrored	Excellent data protection	High cost
10	Mirrored Striped	High performance,	High cost.
		excellent data protection.
5	Parity RAID	Good data protection,	Some performance
		good value	degradation for writes.
Combination	Concatenated	Good performance, low	No data protection
		cost, large Volume size
Single Drive / Segment	Contiguous	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

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