IBM SAS RAID controllers, Manual

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If a disk fails in a RAID 5 array, you can continue to use the array normally. A RAID 5 array that is
operating with a single failed disk is said to be operating in degraded mode. Whenever data is read from
a degraded disk array, the array controller recalculates the data on the failed disk by using data and
parity blocks on the operational disks. If a second disk fails, the array is placed in the failed state and is
not be accessible.
Related information
:
RAID 5 concepts
RAID 6:
Learn how data is written to a RAID 6 array.
RAID 6 stripes data across all disks in the array. RAID level 6 also writes array P and Q parity data. The
P and Q parity data, is spread across all the disks. For a RAID 6 array of four disks, array data and
parity information is written in the following pattern:
Figure 20. RAID 5
SAS RAID controllers for IBM i
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