Avago Technologies MegaRAID SATA 150-4 (523) - Manual (Page 35)

RAID Levels 2-13
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2.4.15 Logical Drive States
The logical drive states are described in Table 2.4 .
2.4.16 Enclosure Management
Enclosure management is the intelligent monitoring of the disk
subsystem by software and/or hardware. The disk subsystem can be part
of the host computer or can reside in an external disk enclosure.
Enclosure management helps you stay informed of events in the disk
subsystem, such as a drive or power supply failure. Enclosure
management increases the fault tolerance of the disk subsystem.
2.5 RAID Levels
The RAID controller supports RAID levels 0, 1, 5, 10, and 50. The
supported RAID levels are summarized in
Section 2.5.1, “Summary of
RAID Levels.” In addition, it supports independent drives (configured as
RAID 0.) The following subsections describe the RAID levels in detail.
2.5.1 Summary of RAID Levels
RAID 0 uses striping to provide high data throughput, especially for large
files in an environment that does not require fault tolerance.
RAID 1 uses mirroring so that data written to one disk drive is
simultaneously written to another disk drive. This is good for small
databases or other applications that require small capacity, but complete
data redundancy.
Table 2.4 Logical Drive States
State Description
Optimal The logical drive operating condition is good. All configured
physical drives are online.
Degraded The logical drive operating condition is not optimal. One of the
configured physical drives has failed or is offline.
Failed The logical drive has failed.
Offline The logical drive is not available to the RAID controller.