HP ProLiant DL280 Configuring Arrays on HP Smart Array Controllers Reference G - Page 111

RAID 50, the failed drives are in different parity groups.

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RAID 50 RAID 50 is a nested RAID method in which the constituent hard drives are organized into several identical RAID 5 logical drive sets (parity groups). The smallest possible RAID 50 configuration has six drives organized into two parity groups of three drives each. For any given number of hard drives, data loss is least likely to occur when the drives are arranged into the configuration that has the largest possible number of parity groups. For example, four parity groups of three drives are more secure than three parity groups of four drives. However, less data can be stored on the array with the larger number of parity groups. RAID 50 is particularly useful for large databases, file servers, and application servers. Advantages: • Higher performance than for RAID 5, especially during writes. • Better fault tolerance than either RAID 0 or RAID 5. • Up to n physical drives can fail (where n is the number of parity groups) without loss of data, as long as the failed drives are in different parity groups. Disadvantages: • All data is lost if a second drive fails in the same parity group before data from the first failed drive has finished rebuilding. • A greater percentage of array capacity is used to store redundant or parity data than with non-nested RAID methods. Drive arrays and fault-tolerance methods 111

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Drive arrays and fault-tolerance methods
111
RAID 50
RAID 50 is a nested RAID method in which the constituent hard drives are organized into several identical
RAID 5 logical drive sets (parity groups). The smallest possible RAID 50 configuration has six drives
organized into two parity groups of three drives each.
For any given number of hard drives, data loss is least likely to occur when the drives are arranged into the
configuration that has the largest possible number of parity groups. For example, four parity groups of three
drives are more secure than three parity groups of four drives. However, less data can be stored on the array
with the larger number of parity groups.
RAID 50 is particularly useful for large databases, file servers, and application servers.
Advantages:
•
Higher performance than for RAID 5, especially during writes.
•
Better fault tolerance than either RAID 0 or RAID 5.
•
Up to
n
physical drives can fail (where
n
is the number of parity groups) without loss of data, as long as
the failed drives are in different parity groups.
Disadvantages:
•
All data is lost if a second drive fails in the same parity group before data from the first failed drive has
finished rebuilding.
•
A greater percentage of array capacity is used to store redundant or parity data than with non-nested
RAID methods.