Compaq 219700-001 - ProLiant - 1500 Reference Manual page 142

Drive Mirroring (RAID 1)
Drive mirroring, also called RAID 1, is the highest performance fault tolerance
method. RAID 1 is the only option offering fault tolerance protection if only two
drives are installed or selected for an array. Drive mirroring creates fault
tolerance by storing two sets of duplicate data on a pair of disk drives. Therefore,
RAID 1 is the most expensive fault tolerance method because 50 percent of the
drive capacity is used to store the redundant data. RAID 1 always requires an
even number of drives. To improve performance in configurations with more
than two drives, the data is striped across the drives. This is also referred to as
RAID 1+0 or RAID 10.
If a drive fails, the mirror drive provides a backup copy of the files and normal
system operations are not interrupted. The mirroring feature requires a minimum
of two drives and, in a multiple drive configuration (four or more drives),
mirroring can withstand multiple simultaneous drive failures as long as the failed
drives are not mirrored to each other.
IMPORTANT:
failed and data loss may occur.
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WAR2-051.AI, 9-1.EPS
Figure D-7. Drive Mirroring stores identical copy of the data
Writer: Pamela King Project: SMART-2DH Array Controller Reference Guide Comments: 295469-002
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COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED
If two drives being mirrored to each other fail, the volume is
DATA
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SMART-2DH Array Controller Reference Guide
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