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HP Smart Array Controllers and basic RAID performance factors

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Figure 8. RAID 1 and RAID 1+0 drive arrays
Write operations for RAID 5
RAID 5 provides data protection by creating a “parity strip.” If any single drive fails, the data from the other drives can be
used to mathematically reconstruct the missing data. Using the data values of the data stripe, the Smart Array uses an
XOR calculation to determine parity. The controller then writes the parity to one of the strips; therefore, RAID 5 requires
the equivalent of one physical drive for storing the parity information. If your array has N number of drives, the array can
store N - 1 drives of data. As shown in Figure 9, the position of the parity strip rotates with each stripe in order to balance
overall performance.
Figure 9. Configuration of a RAID 5 drive array