Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 19)

Understanding RAID Levels and Concepts
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Available RAID Configurations
RAID is a method of combining several hard drives into one unit. It can offer
fault tolerance and higher throughput levels than a single hard drive or group
of independent hard drives. LSI's 3ware controllers support RAID 0, 1, 5, 6,
10, 50, and Single Disk. The following information explains the different
RAID levels.
RAID 0
RAID 0 provides improved performance, but no fault tolerance. Because the
data is striped across more than one disk, RAID 0 disk arrays achieve high
transfer rates because they can read and write data on more than one drive
simultaneously. You can configure the stripe size during unit creation.
RAID 0 requires a minimum of two drives.
When drives are configured in a striped disk array (see Figure 1), large files
are distributed across the multiple disks using RAID 0 techniques.
Striped disk arrays give exceptional performance, particularly for data-
intensive applications such as video editing, computer-aided design, and
geographical information systems.
RAID 0 arrays are not fault tolerant. The loss of any drive results in the loss of
all the data in that array, and can even cause a system hang, depending on
your operating system. RAID 0 arrays are not recommended for high-
availability systems unless you take additional precautions to prevent system
hangs and data loss.
Figure 1. RAID 0 Configuration Example
RAID 1
RAID 1 provides fault tolerance and a speed advantage over non-RAID disks.
RAID 1 also is known as a mirrored array. Mirroring is done on pairs of
drives. Mirrored disk arrays write the same data to two different drives using
RAID 1 algorithms (see Figure 2). This gives your system fault tolerance by
preserving the data on one drive if the other drive fails. Fault tolerance is a
basic requirement for critical systems should as web and database servers.
3ware firmware uses a patented TwinStor technology, on RAID 1 arrays for
improved performance during sequential read operations. With TwinStor