Planning for disk (LUN) ownership assignment

Create a deployment level plan

Before you start configuration, develop a deployment-level plan for software. For example, determine

Which gFilers will own which LUNs on the storage subsystems
Whether you currently need all the storage provided by all the LUNs available to the gFilers or can you leave some LUNs unowned for the present
What your LUN security plan is
What your plan for volumes on the gFiler is

Preventing gFilers and non-gFilers from overwriting LUNs

Use LUN security or switch zoning so that LUNS for gFiler hosts are not visible to non-gFiler hosts, and the reverse. (Whether switch zoning is an effective method depends on the configuration.) The reason is that although the gFiler disk ownership scheme prevents one gFiler from overwriting a LUN owned by another gFiler, it does not prevent a gFiler from overwriting a LUN accessible by a non-gFiler host. Likewise, without a method of preventing overwriting, a non-gFiler host could overwrite a LUN used by a gFiler.

Planning for gFiler volumes

In Data ONTAP, volumes are the primary means of organizing and managing data. You manage data storage by managing volumes. You can think about a volume as a container for the LUNs that provide the capability for data storage.

Each gFiler has a special volume known as a root volume. The root volume is created automatically during the initial setup of the gFiler, after you assign disk (LUN) ownership in the boot menu Maintenance option. The root volume is comprised of one LUN at that time.

If you entered multiple LUNs during initial setup, one LUN, typically the smallest, is automatically selected to be part of the root volume. If the LUNs that you specify are within a plus or minus 20 percent range of each other, the system considers the LUNs to be the same size and randomly picks one of them as the smallest. The other LUNs are allocated as spares. If your organization wants to ensure that the actual smallest LUN is assigned to the root volume, enter only the actual smallest LUN in the boot menu Maintenance option.

Note
You cannot remove the LUN to be selected to be part of the root volume or move it to another volume later. However, after Data ONTAP is installed, you can create another volume, make it the root volume, and destroy the original root volume. See the Data ONTAP Storage Management Guide for more information.

The root volume size is at least 72 GB because 72 GB is required to hold core files and log files that might be generated. You can expand the root volume to 72 GB after initial setup.

After initial setup and Data ONTAP software installation, you can add LUNs to the root volume, or you can create additional volumes and add LUNs to those volumes. Creating multiple volumes provides you the ability to partition your data for management, which you might or might not need.

Note
After you add a LUN to a volume, you cannot remove it.

See Volume configuration and management for volume metrics, considerations for creating multiple volumes, and other information, such as the performance impact of expanding volumes.

Requirement for spare LUNs for a GF270c

Each head of a GF270c must have one spare LUN of 1.5 GB or more assigned to it at all times, in case a problem occurs that results in a panic. The system can then dump core to the spare LUN and NetApp can analyze the core dump to determine the cause of the problem.

Disk (LUN) ownership configuration if you are using local SyncMirror

If you want to deploy the local SyncMirror product to provide synchronous RAID mirroring, you must plan ahead. The reason is that when you configure disk (LUN) ownership, you must correctly configure the pools associated with each LUN so that RAID mirroring works correctly. See Planning for RAID mirroring for data protection for more information.