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Considerations for Data ONTAP RAID groups for array LUNs

Setting up Data ONTAP RAID groups for array LUNs requires planning and coordination with the storage array administrator so that the administrator makes the number and size of array LUNs you need available to Data ONTAP.

For array LUNs, Data ONTAP uses RAID0 RAID groups to determine where to allocate data to the LUNs on the storage array. The RAID0 RAID groups are not used for RAID data protection. The storage arrays provide the RAID data protection.

Note: Data ONTAP RAID groups are similar in concept to what storage array vendors call RAID groups, parity groups, disk groups, Parity RAID groups, and other terms.

Follow these steps when planning your Data ONTAP RAID groups for array LUNs:

  1. Plan the size of the aggregate that best meets your data needs.
  2. Plan the number and size of RAID groups that you need for the size of the aggregate.

    Follow these guidelines:

    • RAID groups in the same aggregate should be the same size with the same number of LUNs in each RAID group. For example, you should create four RAID groups of 8 LUNs each, not three RAID groups of 8 LUNs and one RAID group of 6 LUNs.
    • Use the default RAID group size for array LUNs, if possible. The default RAID group size is adequate for most organizations.
      Note: The default RAID group size is different for array LUNs and disks.
  3. Plan the size of the LUNs that you need in your RAID groups.
    • To avoid a performance penalty, all array LUNs in a particular RAID group should be the same size.
    • The LUNs should be the same size in all RAID groups in the aggregate.
  4. Ask the storage array administrator to create the number of LUNs of the size you need for the aggregate.

    The LUNs should be optimized for performance, according to the instructions in the storage array vendor documentation.

  5. Create all the RAID groups in the aggregate at the same time.
    Note: Do not mix array LUNs from storage arrays with different characteristics in the same Data ONTAP RAID group.
    Note: If you create a new RAID group for an existing aggregate, be sure that the new RAID group is the same size as the other RAID groups in the aggregate, and that the array LUNs are the same size as the LUNs in the other RAID groups in the aggregate.