About automatic assignment of disk ownership

04/02/2024 Contributors

The automatic assignment of unowned disks is enabled by default. Automatic disk ownership assignments occur 10 minutes after HA pair initialization and every five minutes during normal system operation.

When you add a new disk to an HA pair, for example, when replacing a failed disk, responding to a “low spares” message, or adding capacity, the default auto-assignment policy assigns ownership of the disk to a node as a spare.

The default auto-assignment policy is based on platform-specific characteristics, or the DS460C shelf if your HA pair has only these shelves, and it uses one of the following methods (policies) to assign disk ownership:

Assignment method	Effect on node assignments	Platform configurations that default to the assignment method
bay	Even-numbered bays are assigned to node A and odd-numbered bays to node B.	Entry-level systems in an HA pair configuration with a single, shared shelf.
shelf	All disks in the shelf are assigned to node A.	Entry-level systems in an HA pair configuration with one stack of two or more shelves, and MetroCluster configurations with one stack per node, two or more shelves.
split shelf This policy falls under the “default” value for the `-autoassign-policy` parameter of the `storage disk option` command for applicable platform and shelf configurations.	Disks on the left side of the shelf are assigned to node A and on the right side to Node B. Partial shelves on HA pairs are shipped from the factory with disks populated from the shelf edge toward the center.	Most AFF platforms and some MetroCluster configurations.
stack	All disks in the stack are assigned to node A.	Stand-alone entry-level systems and all other configurations.
half-drawer This policy falls under the “default” value for the `-autoassign-policy` parameter of the `storage disk option` command for applicable platform and shelf configurations.	All drives in the left half of a DS460C drawer (drive bays 0 to 5) are assigned to node A; all drives in the right half of a drawer (drive bays 6 to 11) are assigned to node B. When initializing an HA pair with only DS460C shelves, automatic assignment of disk ownership is not supported. You must manually assign ownership for drives containing root/container drives that have the root partition by conforming to the half-drawer policy.	HA pairs with only DS460C shelves, after HA pair initialization (boot up). After an HA pair boots up, automatic assignment of disk ownership is automatically enabled and uses the half-drawer policy to assign ownership to the remaining drives (other than the root drives/container drives that have the root partition) and any drives added in the future. If your HA pair has DS460C shelves in addition to other shelf models, the half-drawer policy is not used. The default policy used is dictated by platform-specific characteristics.

Assignment method

Effect on node assignments

Platform configurations that default to the assignment method

bay

Even-numbered bays are assigned to node A and odd-numbered bays to node B.

Entry-level systems in an HA pair configuration with a single, shared shelf.

shelf

All disks in the shelf are assigned to node A.

Entry-level systems in an HA pair configuration with one stack of two or more shelves, and MetroCluster configurations with one stack per node, two or more shelves.

split shelf

This policy falls under the “default” value for the -autoassign-policy parameter of the storage disk option command for applicable platform and shelf configurations.

Disks on the left side of the shelf are assigned to node A and on the right side to Node B. Partial shelves on HA pairs are shipped from the factory with disks populated from the shelf edge toward the center.

Most AFF platforms and some MetroCluster configurations.

stack

All disks in the stack are assigned to node A.

Stand-alone entry-level systems and all other configurations.

half-drawer

This policy falls under the “default” value for the -autoassign-policy parameter of the storage disk option command for applicable platform and shelf configurations.

All drives in the left half of a DS460C drawer (drive bays 0 to 5) are assigned to node A; all drives in the right half of a drawer (drive bays 6 to 11) are assigned to node B.

When initializing an HA pair with only DS460C shelves, automatic assignment of disk ownership is not supported. You must manually assign ownership for drives containing root/container drives that have the root partition by conforming to the half-drawer policy.

HA pairs with only DS460C shelves, after HA pair initialization (boot up).

After an HA pair boots up, automatic assignment of disk ownership is automatically enabled and uses the half-drawer policy to assign ownership to the remaining drives (other than the root drives/container drives that have the root partition) and any drives added in the future.

If your HA pair has DS460C shelves in addition to other shelf models, the half-drawer policy is not used. The default policy used is dictated by platform-specific characteristics.

Auto-assignment settings and modifications:

You can display the current auto-assignment settings (on/off) with the storage disk option show command.
You can disable automatic assignment by using the storage disk option modify command.
If the default auto-assignment policy is not desirable in your environment, you can specify (change) the bay, shelf, or stack assignment method using the -autoassign-policy parameter in the storage disk option modify command.

Learn how to Change settings for automatic assignment of disk ownership.

The half-drawer and split-shelf default auto-assignment policies are unique because they cannot be set by users like the bay, shelf, and stack policies can.

In Advanced Drive Partitioning (ADP) systems, to make auto-assign work on half-populated shelves, drives must be installed in the correct shelf bays based on what type of shelf you have:

If your shelf is not a DS460C shelf, install drives equally on the far left side and far right side moving toward the middle. For example, six drives in bays 0-5 and six drives in bays 18-23 of a DS224C shelf.
If your shelf is a DS460C shelf, install drives in the front row (drive bays 0, 3, 6, and 9) of each drawer. For the remaining drives, evenly distribute them across each drawer by filling drawer rows from front to back. If you don’t have enough drives to fill rows, then install them in pairs so that drives occupy the left and right side of a drawer evenly.

Installing drives in the front row of each drawer allows for proper air flow and prevents overheating.

If drives are not installed in the correct shelf bays on half-populated shelves, when a container drive fails and is replaced, ONTAP does not auto-assign ownership. In this case, assignment of the new container drive needs to be done manually. After you have assigned ownership for the container drive, ONTAP automatically handles any drive partitioning and partitioning assignments that are required.

In some situations where auto-assignment will not work, you need to manually assign disk ownership using the storage disk assign command:

If you disable auto-assignment, new disks are not available as spares until they are manually assigned to a node.
If you want disks to be auto-assigned and you have multiple stacks or shelves that must have different ownership, one disk must have been manually assigned on each stack or shelf so that automatic ownership assignment works on each stack or shelf.
If auto-assignment is enabled and you manually assign a single drive to a node that isn’t specified in the active policy, auto-assignment stops working and an EMS message is displayed.

Learn how to Manually assign disk ownership of unpartitioned disks.

Learn how to Manually assign disk ownership of partitioned disks.

About automatic assignment of disk ownership

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