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RAID protection levels for disks
Data ONTAP supports two levels of RAID protection for disks in native disk shelves, RAID-DP and RAID4. RAID-DP can protect against double-disk failures or failures during reconstruction. RAID4 can protect against single-disk failures. You assign RAID level on a per-aggregate basis.
For more information about choosing RAID protection levels, see Technical Report 3437: Storage Best Practices and Resiliency Guide.
Related Link:  
TR 3437: Storage Best Practices and Resiliency Guide