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.
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
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. Below are some common RAID functions:
- 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 to work on
Components and Features
Drive Group
A drive group is a group of physical drives. These drives are managed in partitions known as virtual drives.
Virtual Drive
A virtual drive is a partition in a drive group that is made up of contiguous data segments on the drives. A virtual drive can consist of an entire drive group, more than one entire drive group, a part of a drive group, parts of more than one drive group, or a combination of any two of these conditions.
Fault Tolerance
Fault tolerance is the capability of the subsystem to undergo a drive failure or failures without compromising data integrity, and processing capability. The RAID controller provides this support through redundant drive groups in RAID levels 1, 5, 6, 10, 50, and 60. The system can still work properly even with drive failure in a drive group, though performance can be degraded to some extent. In a span of RAID 1 drive groups, each RAID 1 drive group has two drives and can tolerate one drive failure. The span of RAID 1 drive groups can contain up to 32 drives, and tolerate up to 16 drive failures - one in each drive group. A RAID 5 drive group can tolerate one drive failure in each RAID 5 drive group. A RAID 6 drive group can tolerate up to two drive failures. Each spanned RAID 10 virtual drive can tolerate multiple drive failures, as long as each failure is in a separate drive group. A RAID 50 virtual drive can tolerate two drive failures, as long as each failure is in a separate drive group. RAID 60 drive groups can tolerate up to two drive failures in each drive group