Owner's manual

12 Overview
About RAID
RAID is a group of multiple independent physical disks that provide high
performance or better data availability by increasing the number of drives
used for saving and accessing data. A RAID disk subsystem improves
I/O performance and data availability. The physical disk group appears to the
host system as a single storage unit. Data throughput improves because
multiple disks can be accessed simultaneously. RAID systems also improve
data storage availability and fault tolerance.
RAID Levels
RAID 0 uses disk striping to provide high data throughput, especially for large
files in an environment that requires no data redundancy.
Integrated Mirroring or RAID 1 uses disk mirroring so that data written to
one physical disk is simultaneously written to another physical disk. This is
good for small databases or other applications that require small capacity, but
complete data redundancy.
NOTICE: Lost data on an Integrated Striping virtual disk cannot be recovered in the
event of a physical disk failure.
RAID Terminology
Integrated Striping
Integrated Striping (RAID 0) allows you to write data across multiple physical
disks instead of just one physical disk. Integrated Striping involves partitioning
each physical disk storage space into 64 KB stripes. These stripes are
interleaved in a repeated sequential manner. The part of the stripe on a single
physical disk is called a stripe element.
For example, in a four-disk system using only Integrated Striping, segment 1 is
written to disk 1, segment 2 is written to disk 2, and so on. Integrated Striping
enhances performance because multiple physical disks are accessed
simultaneously, but Integrated Striping does not provide data redundancy.
Figure 2-2 shows an example of Integrated Striping.
book.book Page 12 Monday, September 15, 2008 2:47 PM