LSI MegaRAID Express 500 - Manual (Page 22)

MegaRAID Express 500 Hardware Guide 8
RAID Overview
RAID (Redundant Array of Independent Disks) is a collection of specifications that
describe a system for ensuring the reliability and stability of data stored on large disk
subsystems. A RAID system can be implemented in a number of different versions (or
RAID Levels). The standard RAID levels are 0, 1, 3, and 5. MegaRAID Express 500
supports all standard RAID levels and RAID levels 10, 30, and 50, special RAID versions
supported by MegaRAID Express 500.
Fault Tolerance
Fault tolerance is achieved through cooling fans, power supplies, and the ability to hot
swap drives. MegaRAID Express 500 provides hot swapping through the hot spare
feature. A hot spare drive is an unused online available drive that MegaRAID Express
500 instantly plugs into the system when an active drive fails.
After the hot spare is automatically moved into the RAID subsystem, the failed drive is
automatically rebuilt. The RAID disk array continues to handle request while the rebuild
occurs.
Consistency Check
In RAID, check consistency verifies the correctness of redundant data in an array. For
example, in a system with dedicated parity, checking consistency means computing the
parity of the data drives and comparing the results to the contents of the dedicated parity
drive.