Avago Technologies MegaRAID Fast Path Software - Manual (Page 21)

LSI Corporation Confidential | July 2011 Page 21
MegaRAID SAS Software User Guide Chapter 2: Introduction to RAID | RAID Description
Chapter 2
2.1 RAID Description RAID is an array, or group, of multiple independent physical drives that provide high
performance and fault tolerance. A RAID drive group improves I/O (input/output)
performance and reliability. The RAID drive group appears to the host computer as a
single storage unit or as multiple virtual units. I/O is expedited because several drives
can be accessed simultaneously.
2.2 RAID Benefits RAID drive groups improve data storage reliability and fault tolerance compared to
single-drive storage systems. Data loss resulting from a drive failure can be prevented
by reconstructing missing data from the remaining drives. RAID has gained popularity
because it improves I/O performance and increases storage subsystem reliability.
2.3 RAID Functions Virtual drives are drive groups or spanned drive groups that are available to the
operating system. The storage space in a virtual drive is spread across all of the drives in
the drive group.
Your drives must be organized into virtual drives in a drive group, and they must be
able to support the RAID level that you select. Some common RAID functions follow:
 Creating hot spare drives
 Configuring drive groups and virtual drives
 Initializing one or more virtual drives
 Accessing controllers, virtual drives, and drives individually
 Rebuilding failed drives
 Verifying that the redundancy data in virtual drives using RAID level 1, 5, 6, 10, 50, or
60 is correct
 Reconstructing virtual drives after changing RAID levels or adding a drive to a drive
group
 Selecting a host controller on which to work
Introduction to RAID
This chapter describes Redundant Array of Independent Disks (RAID), RAID functions
and benefits, RAID components, RAID levels, and configuration strategies. In addition, it
defines the RAID availability concept, and offers tips for configuration planning.