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Considerations for automatic drive assignment and ADP systems

MetroCluster IP configurations support new installations with AFA systems using ADP (Advanced Drive Partitioning). In most configurations, partitioning and disk assignment is performed automatically during the initial configuration of the MetroCluster sites.

ONTAP 9.4 and later releases include the following changes for ADP support:

  • Pool 0 disk assignments are done at the factory.

  • The unmirrored root is created at the factory.

  • Data partition assignment is done at the customer site during the setup procedure.

  • In most cases, drive assignment and partitioning is done automatically during the setup procedures.

Note
When upgrading from ONTAP 9.4 to 9.5, the system recognizes the existing disk assignments.

Automatic partitioning​

ADP is performed automatically during initial configuration of the platform.

Note
Starting with ONTAP 9.5, disk autoassignment must be enabled for automatic partitioning for ADP to occur.

How shelf-by-shelf automatic assignment works​

If there are four external shelves per site, each shelf is assigned to a different node and different pool, as shown in the following example:

  • All of the disks on site_A-shelf_1 are automatically assigned to pool 0 of node_A_1

  • All of the disks on site_A-shelf_3 are automatically assigned to pool 0 of node_A_2

  • All of the disks on site_B-shelf_1 are automatically assigned to pool 0 of node_B_1

  • All of the disks on site_B-shelf_3 are automatically assigned to pool 0 of node_B_2

  • All of the disks on site_B-shelf_2 are automatically assigned to pool 1 of node_A_1

  • All of the disks on site_B-shelf_4 are automatically assigned to pool 1 of node_A_2

  • All of the disks on site_A-shelf_2 are automatically assigned to pool 1 of node_B_1

  • All of the disks on site_A-shelf_4 are automatically assigned to pool 1 of node_B_2

Manual drive assignment (ONTAP 9.5)​

In ONTAP 9.5, manual drive assignment is required on systems with the following shelf configurations:

  • Three external shelves per site.

    Two shelves are assigned automatically using a half-shelf assignment policy, but the third shelf must be assigned manually.

  • More than four shelves per site and the total number of external shelves is not a multiple of four.

    Extra shelves above the nearest multiple of four are left unassigned and the drives must be assigned manually. For example, if there are five external shelves at the site, shelf five must be assigned manually.

You only need to manually assign a single drive on each unassigned shelf. The rest of the drives on the shelf are then automatically assigned.

Manual drive assignment (ONTAP 9.4)​

In ONTAP 9.4, manual drive assignment is required on systems with the following shelf configurations:

  • Fewer than four external shelves per site.

    The drives must be assigned manually to ensure symmetrical assignment of the drives, with each pool having an equal number of drives.

  • More than four external shelves per site and the total number of external shelves is not a multiple of four.

    Extra shelves above the nearest multiple of four are left unassigned and the drives must be assigned manually.

When manually assigning drives, you should assign disks symmetrically, with an equal number of drives assigned to each pool. For example, if the configuration has two storage shelves at each site, you would one shelf to the local HA pair and one shelf to the remote HA pair:

  • Assign half of the disks on site_A-shelf_1 to pool 0 of node_A_1.

  • Assign half of the disks on site_A-shelf_1 to pool 0 of node_A_2.

  • Assign half of the disks on site_A-shelf_2 to pool 1 of node_B_1.

  • Assign half of the disks on site_A-shelf_2 to pool 1 of node_B_2.

  • Assign half of the disks on site_B-shelf_1 to pool 0 of node_B_1.

  • Assign half of the disks on site_B-shelf_1 to pool 0 of node_B_2.

  • Assign half of the disks on site_B-shelf_2 to pool 1 of node_A_1.

  • Assign half of the disks on site_B-shelf_2 to pool 1 of node_A_2.

Adding shelves to an existing configuration.​

Automatic drive assignment supports the symmetrical addition of shelves to an existing configuration.

When new shelves are added, the system applies the same assignment policy to newly added shelves. For example, with a single shelf per site, if an additional shelf is added, the systems applies the quarter-shelf assignment rules to the new shelf.

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