• It is useful when data protection and usable capacity are more important than write performance.
• It allows any two drives to fail without loss of data.
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.
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.
This method has the following benefits:
• 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.
RAID 60
RAID 60 is a nested RAID method in which the constituent hard drives are organized into several
identical RAID 6 logical drive sets (parity groups). The smallest possible RAID 60 configuration has eight
drives organized into two parity groups of four 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, five parity groups of
four drives are more secure than four parity groups of five drives. However, less data can be stored on
the array with the larger number of parity groups.
Hardware issues
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