User`s guide

CAP Strategy for Selecting a RAID Level
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tolerance. RAID 3 and RAID 5 give the next best capacity, followed by RAID 1 and RAID
0+1.
Configuring for Maximum Availability
Table 4-3 presents definitions of array operating conditions.
You can achieve an additional measure of fault tolerance (or improved availability) with
a hot spare, or standby disk drive. This disk drive is powered on but idle during normal
array operation. If a failure occurs on a disk drive in a fault-tolerant set, the hot spare
takes over for the failed disk drive, and the array continues to function in a fully
fault-tolerant mode after it completes its automatic rebuild cycle. Thus the array can
suffer a second disk drive failure after rebuild and continue to function before any disk
drives are replaced.
Table 4-3 Array Operating Conditions
Array Condition Meaning
Normal (online) The array is operating in a fault-tolerant mode, and can sustain a disk drive failure without
data loss.
Critical The array is functioning and all data is available, but the array cannot sustain a second disk
drive failure without potential data loss.
Degraded The array is functioning and all data is available, but the array cannot sustain a second disk
drive failure without potential data loss. Additionally, a reconstruction or rebuild operation is
occurring, reducing the performance of the array. The rebuild operation takes the array from a
critical condition to a normal condition.
Offline The array is not functioning. If the array is configured with a redundant RAID level, two or
more of its member disk drives are not online. If the array is configured as a RAID 0 or JBOD,
one or more of its member disk drives are not online.
Not fault-tolerant No fault-tolerant RAID levels have been configured for any of the disk drives in the array.