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NetApp Knowledge Base

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

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disk-drives
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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

  • Adding fewer than the recommended drives above might impact the performance of some write-intensive workloads
  • While changing the maximum RAID size of an aggregate beyond its default size can be used to accommodate more drives in existing RAID groups, doing so might have implications.  If creating new RAID groups or adding to existing or resized RAID groups:
  • Right sized drives can be replaced via storage disk replace if a more appropriate spare is available