Rules for the disk (LUN) ownership software scheme

Facts about disk (LUN) ownership

The following rules apply to the gFiler disk (LUN) ownership scheme:

You can configure only one gFiler to own a specific disk (LUN).
During initial setup of the gFiler, you must identify at least one disk (LUN). Otherwise, you cannot set up the gFiler.
After you perform the initial setup of your gFiler, you can add additional LUNs that the gFiler is to own. See Managing LUNs and LUN ownership for more information.
A LUN must be part of a volume for it to be used for data storage.
You might want the LUN to be part of the root volume or part of a different volume that you create later. See Planning for disk (LUN) ownership assignment for information about how the system handles LUNs if you enter multiple LUNs during the initial setup.
Until the LUN that a gFiler owns is configured to be part of a volume, it is a spare LUN.
You can remove all ownership status of a LUN by a gFiler. If you do so, the content of the LUN is not affected because disk (LUN) ownership is a logical relationship. The gFiler can no longer access the LUN after ownership status is removed, however. See Managing LUNs and LUN ownership for information about removing ownership status of a LUN.
In most circumstances, if you want to move data service from one gFiler to another, you need to set up your gFiler to support the SnapMover^TM and MultiStore^TM vFiler products. Through SnapMover, you can move the volume in which the LUN resides. See Chapter 7, Planning for using SnapMover to change workload distribution for more information.
Not all LUNs that the storage subsystems make available for the gFilers must be owned. From the point of view of Data ONTAP, a LUN that is unowned is not a spare LUN; a spare is owned by the gFiler.

The following scenarios summarize the rules in the previous list from a configuration point of view.

Viewing disk (LUN) ownership from a configuration point of view

Scenario 1--disk ownership is not configured yet

In this scenario, the LUNs have been made available (visible) on the storage subsystem. However, gFiler 1 has not yet been configured for disk (LUN) ownership. Therefore, the gFiler cannot read data from or write data to any LUNs on the storage subsystem.

Scenario--only some LUNs are owned

In this scenario, gFiler 1 has been configured to own LUNs 1 and 2, but not LUNs 3 and 4, because LUNs 3 and 4 are not yet needed for storage. The smallest of the two LUNs was automatically assigned to the root volume during initial setup of the gFiler. The other LUN was automatically allocated as a spare and remains a spare until you add it to a volume after Data ONTAP software installation; gFiler 1 can read data from and write data only to LUN 1 until LUN 2 is configured to be part of a volume.

After you perform initial setup of the gFiler, you could configure gFiler 1 to own LUN 3, LUN 4, or both. See Managing LUNs and LUN ownership.

Scenario 3--configuration with a cluster

In this scenario, two gFilers are configured in a cluster and the two gFilers share the same storage subsystem.

Assume that during initial setup gFiler 1 was assigned ownership of LUN 1 and LUN 2. LUN 1 was automatically added to the root volume, so the gFiler can access it for storage. LUN 2 remains a spare until you explicitly add it to a volume after Data ONTAP installation.

Similarly, assume that during initial setup gFiler 2 was assigned ownership of LUN 3 and LUN 4. LUN 4 remains a spare until you explicitly add it to a volume after Data ONTAP installation.

The key points of this scenario are as follows:

Only one gFiler can own a specific LUN.
By deploying the gFilers in a cluster, one gFiler can take over services for the other if a gFiler becomes unavailable.
By deploying two switches, if one switch fails, the other switch provides the alternate path to the storage subsystem.

Command for adding disk (LUN) ownership

The command used for assigning disk (LUN) ownership is disk assign. See Chapter 4, Installing Data ONTAP Software for its use during initial setup of the gFiler and Chapter 6, Managing Volumes, RAID Groups, and LUNs for its use after initial setup.