IBM N series Hardware Manual page 182

Figure 10-23 shows a completed conversion to RAID-DP volume.
Figure 10-23 The itso volume completed RAID-DP conversion successfully
Converting existing aggregates and traditional volumes back to RAID4
Aggregates and traditional volumes can be converted back to RAID4 with the [aggr |vol]
options name raidtype raid4 command. Figure 10-24 shows itso as RAID-DP parity.
Figure 10-24 Aggregate status of itso as RAID-DP parity
Figure 10-25 shows the conversion of itso back to RAID4. In this case, the conversion is
instantaneous because the old RAID4 row parity construct is still in place as a subsystem in
RAID-DP.
Figure 10-25 The itso volume conversion from traditional RAID-DP to RAID4
Figure 10-26 shows the completed process. If a RAID-DP group is converted to RAID4, each
RAID group's second diagonal parity disk is released and put back into the spare disk pool.
Figure 10-26 RAID4 conversion instantaneous completion results
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IBM System Storage N series Hardware Guide