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Does ONTAP allow mixing of drive sizes in a RAID group?

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Applies to

  • All FAS systems
  • All AFF systems
  • ONTAP
  • Disk drive types: SSD, SAS, NL-SAS

Answer

  • Yes, ONTAP allows mixing of different drive physical sizes in any RAID group
  • When adding larger drives to an existing RAID group of smaller drives, the larger drives will be right sized to match the usable capacity of the smaller drives.
    For example:
    • Adding a 10TB NL-SAS drive to an existing RAID group of 4TB drives results in usable capacity of 3.63TB on the 10TB drive. 
      NOTE: ​​​Right sizing applies to DATA drives.  It is possible for PARITY drives to not be right sized, but additional added DATA drives will continue to be right sized
  • When adding 10TB or 16TB drives to an existing RAID group of smaller drives, ONTAP does not require RAID-TEC to be used.  This is because the usable capacity of the drive is being reduced to less than the drive capacity maximum specified by NetApp Hardware Universe.
  • To avoid possible performance issues, the minimum number of larger drives that should be added to existing RAID groups are: 
    • SSDs - minimum of 2 drive 
    • SAS, NL-SAS - minimum of 6 drives 
  • Provided these guidelines are followed, there is no performance penalty for mixing drive capacities in the same RAID group.

Additional Information

 

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