Volume configuration and management

About volumes

In Data ONTAP, volumes are the primary means of organizing and managing data. You can think about a NetApp Data ONTAP volume as a container for storing data. You identify the collection of LUNs that are to be in the volume (where collection could mean only one LUN); those LUNs provide the capability for data storage. You manage data storage by managing volumes through the Data ONTAP system administration interface.

During the initial setup process, a root volume is automatically created (see Planning for disk (LUN) ownership assignment). However, you can create multiple volumes to facilitate data management. For example, you could create additional volumes to accommodate your users if they speak more than one language, such as one volume for data in French and another for data in German.

The Data ONTAP System Administration Storage Management Guide provides more details about procedures for managing volumes than are provided in this section. This section provides specific information about volumes with the gFiler.

Volume metrics

The following table summarizes volume metrics for gFilers.

Metric	Information
Maximum number of volumes on a gFiler	200 volumes for both clustered and single gFilers
Minimum root volume size	72 GB (72 GB is required to hold core files and log files that might be generated.)
Minimum size for a non-root volume	1 GB (the same as the minimum size for a LUN)
Maximum volume size	This is dependent on the gFiler model. See the gFiler Gateway Series Getting Started Guide.
Number of LUNs in a volume	See Guidelines for determining volume size.
Maximum number of RAID groups in a volume	150 RAID groups. See Management of RAID groups associated with NetApp volumes for information about the role of RAID groups with volumes. Caution If you exceed the maximum volume size or maximum capacity for a gateway model, the maximum RAID groups in a volume is less than 150.

Guidelines for determining volume size

To determine the volume size, you must first determine the amount of space that you need to store data. Then specify the number of LUNs that you need for the capacity and performance that you require. Factors to consider are as follows:

Capacity
How many LUNs you need to specify to support the storage capacity of the volume:
- Consider the size of LUNs that were created on the storage subsystem.
- Consider that the more LUNs you add to a volume, the more space is available.
- Consider the maximum volume size for your gFiler model. See the gFiler Gateway Series Getting Started Guide for more information.
- Consider the total number of LUNs for your gFiler model. See the gFiler Gateway Series Getting Started Guide for more information.
Performance
How many LUNs are required for adequate I/O performance

Moving or deleting LUNs

After a LUN becomes part of a volume, the LUN cannot be moved to another volume or deleted. You can only move volumes, destroy volumes, or expand volumes. If you destroy a volume, all data in the volume is destroyed and is no longer accessible. See Chapter 7, Managing Workload Distribution with SnapMover for more information about moving volumes by using SnapMover.

Should you add LUNs to a volume or create additional volumes?

If a volume has not reached its maximum number of LUNs, you can add LUNs to a volume.

If the gFiler volume was fully allocated with user data before you added LUNs to the volume, most of the free space for write actions is obtained from the new LUNs after the new LUNs are added. Therefore, add enough LUNs at the same time so that the system does not become spindle bound for the write actions. In general, adding two or more LUNs to a volume at the same time should satisfy this requirement.

Other than the performance issue just mentioned, there are no performance penalties that result from expanding an existing volume.

There is no performance penalty for expanding a volume with a different-sized LUN, as long as the new RAID group on the gFiler is created with the newly added LUN. See What to do if you are expanding a volume with a different-sized LUN.

Importance of volume names for migration

Consider whether you might need to move a volume in the future. If so, take care that names of volumes on the different gFilers are different. If you need to move volumes with vFilers later through SnapMover, the names of the vFilers and volumes being moved from the source to the destination must be unique. See Planning for using SnapMover to change workload distribution for more information

Creating a volume

To create a volume, complete the following steps.

Note
See the Data ONTAP Storage Management Guide for details about creating mirrored volumes.

Step	Action
1	View a list of the spare LUNs on your NetApp appliance. At the gFiler console, enter the following command: `vol status -s` Result The output of `vol status -s` lists all the spare LUNs that you can select for inclusion in the volume and their capacities.
2	At the system prompt, enter the following command: vol create vol-name [-r raid-group-size] [-l language_code] disk-list vol-name is the name for the new volume (without the /vol/ prefix). raid-group-size is the size of the RAID group you want. language_code specifies a language other than that of the root volume. See the Data ONTAP Storage Management Guide for a list of language codes. disk-list is one of the following: ndisks[@disk-size] ndisks is the number of LUNs in the volume. The value of ndisks must be at least 1 for unmirrored volumes and 2 for mirrored volumes. disk-size is the LUN size to use, in gigabytes. You must have at least ndisk available LUNs of the size you specify. Data ONTAP will select LUNs within a plus or minus 20 percent range of the size you enter. `-d` disk_name1 disk_name2... disk_nameN disk_name1, disk_name2, and disk_nameN are IDs of one or more LUNs that the gFiler owns; use a space to separate multiple LUNs.
3	Enter the following command to verify that the volume exists as you specified: *vol status vol_name* -r** vol_name is the name of the volume whose existence you want to verify. Result: The system displays the RAID groups and LUNs of the specified volume on your gFiler.
4	If you have...	Then...
	An NFS-only gFiler	Go to Step 6.
	A CIFS-only or multiprotocol gFiler	Create shares that refer to the new volume to enable clients to access it, then go to Step 5.
5	If you have...	Then...
	A CIFS-only gFiler	You are done.
	A multiprotocol gFiler	Go to Step 6.
6	Update the system /etc/exports file with the new volume.
7	Run `exportfs`.
8	Add the appropriate mount point information to the /etc/fstab or /etc/vfstab file on clients that mount volumes from the gFiler.

Volume creation examples

Example 1

The following command creates a volume called newvol, with no more than eight LUNs in a RAID group, using the French character set, consisting of the LUNs with IDs 8a.0L4, 8a.0L2, and 8a.0L5.

vol create newvol -r 8 -l fr -d 8a.0L4 8a.0L2 8a.0L5

Example 2

The following command creates the volume newvol. The RAID group size is 14 LUNs. Because the volume consists of 28 LUNs, those LUNs form two RAID groups, rg0 and rg1:

vol create newvol -r 14 28@36

Parameters to accept or change after volume creation

After you create a volume, you can accept the defaults for CIFS oplocks and security style settings or change the values. You should decide what to do as soon as possible after creating the volume. If you change the parameters after files are in the volume, they might become inaccessible to users because of conflicts between the old and new values. For example, UNIX files available under mixed security might not be available after you change to NTFS security.

CIFS oplocks setting

The CIFS oplocks setting determines whether the volume uses CIFS oplocks. The default is to use CIFS oplocks.

Security style

The security style determines whether the files in a volume use NTFS security, UNIX security, or both.

With a new gFiler, the default depends on what protocols you licensed, as shown in the following table.

Protocol licenses	Default volume security style
CIFS only	NTFS
NFS only	UNIX
CIFS and NFS	UNIX

See the Data ONTAP Storage Management Guide for information about the security style.