Considerations for automatic drive assignment and ADP systems in ONTAP 9.4 and later

Starting with ONTAP 9.4, MetroCluster IP configurations support new installations with AFF 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:

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:

How to populate partially-full shelves

If your configuration is using shelves that are not fully populated (have empty drive bays) you must distribute the drives evenly throughout the shelf, depending on the disk assignment policy. The disk assignment policy depends on how many shelves are at each MetroCluster site.

If you are using a single shelf at each site (or just the internal shelf on an AFF A800 system), disks are assigned using a quarter-shelf policy. If the shelf is not fully populated, install the drives equally on all quarters.

The following table shows an example of how to place 24 disks in a 48 drive internal shelf. The ownership for the drives is also shown.

The 48 drive bays are divided into four quarters: Install six drives in the first six bays in each quarter...
Quarter 1: Bays 0 -11 Bays 0-5
Quarter 2: Bays 12-23 Bays 12-17
Quarter 3: Bays 24-35 Bays 24-29
Quarter 4: Bays 36-48 Bays 36-41

If you are using two shelves at each site, disks are assigned using a half-shelf policy. If the shelves are not fully populated, install the drives equally from either end of the shelf.

For example, if you are installing 12 drives in a 24 drive shelf, install drives in bays 0-5 and 18-23.

Manual drive assignment (ONTAP 9.5)

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

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:

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.