IBM Storwize V5010 Manual page 200

When you are satisfied with the presented configuration click Assign as shown in
Figure 4-48. The array MDisks are then created and initialized on the background.
Figure 4-48 Clicking assign on quick configuration wizard
Advanced internal custom configuration
Selecting Internal Custom allows the user to customize the configuration for internal drives.
Tip: It is advised to use the advanced configuration only when the quick configuration
suggested does not fit your business requirements.
The following values can be customized:
RAID level
Number of spares
Array width
Stripe width
Number of drives of each class
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Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1