Avago Technologies MegaRAID SATA 150-4 (523) - Manual (Page 25)

RAID Components and Features 2-3
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2.4 RAID Components and Features
RAID levels describe a system for ensuring the availability and
redundancy of data stored on large disk subsystems. See
Section 2.5,
“RAID Levels,” page 2-13 for detailed information about RAID levels.
2.4.1 Physical Array
A physical array is a group of physical disk drives. The physical disk
drives are managed in partitions known as logical drives.
2.4.2 Logical Drive
A logical drive is a partition in a physical array of disks that is made up
of contiguous data segments on the physical disks. A logical drive can
consist of an entire physical array, more than one entire physical array, a
part of an array, parts of more than one array, or a combination of any
two of these conditions.
Note: The maximum logical drive size for all supported RAID
levels (0, 1, 5, 10, and 50) is 2 Tbytes. You can create
multiple logical drives within the same physical array.
2.4.3 RAID Array
A RAID array is one or more logical drives controlled by the RAID
controller.
2.4.4 Fault Tolerance
Fault tolerance is the capability of the subsystem to undergo a single
failure without compromising data integrity, and processing capability.
The RAID controller provides this support through redundant arrays in
RAID levels 1, 5, 10 and 50. The system can still work properly even with
a single disk failure in an array, through performance can be degraded
to some extent.
Note: RAID level 0 is not fault-tolerant. If a drive in a RAID 0 array
fails, the whole logical drive (all physical drives associated
with the logical drive) fails.