Volume concepts

Section contents

This section covers the following topics:

• Understanding volumes
• Determining the number of volumes to use
• Planning a multiple volume configuration
• Installing a foreign volume

Understanding volumes

Data on the filer is organized in volumes. A volume is an independent file system with its own RAID groups.

The initial configuration for new filers running Data ONTAP 5.0 or later includes one 2- to 14-disk volume (a root file system). All remaining disks are spares.

Volume naming conventions

You choose the volume names. The names must follow these naming conventions:

• begin with either a letter or an underscore (_)
• contain only letters, digits, and underscores
• contain no more than 255 characters

The root volume

Each filer must have a root volume to boot. The root volume of a filer (configured with either a single volume or multiple volumes) is the volume whose /etc directory is used by the filer for configuration information.

The filer uses two naming conventions to indicate the root volume:

• /vol/vol0
• /

In the /vol/vol0 convention

For backward compatibility with filers running releases of Data ONTAP earlier than 5.0, you can use the / naming convention to indicate the root volume on a filer that you upgraded to Data ONTAP 5.1 that contains a previously existing file system.

Mounting volumes

On filers configured with multiple volumes, mounting / is equivalent to mounting /vol/vol0/, (where vol0 is the root directory of the root volume). Paths that begin with / (for example, /etc) refer to directories on the root volume.

Note: /vol is not a directory--it is a special virtual root path under which the filer mounts other directories. You cannot mount /vol to view all the volumes on the filer; you must mount each filer volume separately.

In mount requests and server commands, prefix the path names of the volumes and directories you want to mount using the convention /vol/volume_name/directory.

Example

For example, /vol/users/home/cheryl is a directory called /home/cheryl in a volume named users.

Determining the number of volumes to use

Whether you should use the default single volume configuration or create additional volumes depends mainly on the storage capacity of the filer.

Use of a single volume

If you want the filer to be configured with a single volume, you do not need to do any further volume configuration after you complete the initial setup.

If your filer doesn't have a large number of disks, a single-volume configuration is probably all you need. You can create additional volumes in the future.

Use of multiple volumes

There are several factors to consider before deciding to create and use multiple volumes:

Configuring with multiple volumes aids in the administration of filers that have large storage capacities, enabling you to

• Perform administrative and maintenance tasks, for example, backup and restore, on individual volumes rather than on a single, large file system.
• Set option command values, for example, snap sched, raidsize, minra, no_atime_update, and so on, differently for individual volumes.
• Take individual volumes off-line, for example, to perform administrative tasks on their file systems or associated RAID groups, while the other volumes remain on-line, without interrupting the availability of the data on them.

Limitations of configuring with multiple volumes include

• The filer's storage space is partitioned.
• Additional administrative overhead is introduced, for example, defining export points.
• You can expand but not concatenate, shrink, or split volumes.
• You cannot perform a local copy of a volume's contents; you must use dump and restore or ndmp copy.

Planning a multiple volume configuration

Before you configure a filer with multiple volumes, you must decide on the number and sizes of volumes you want to configure.

When deciding the number and sizes of volumes you want to configure, keep the following considerations in mind:

• Configuring with more volumes
  • provides more flexible quota and snapshot configuration
  • requires more export points
• Configuring with larger volumes increases the time needed to restore a volume from tape.
• The maximum number of volumes per filer is 23.
• The maximum recommended volume size is 250 GB.

For instructions about specific volume configuration procedures, see "Volume management tasks."

Installing a foreign volume

You can remove an entire volume from one filer and install it in another, which makes the moved volume a foreign volume to the filer.

Example

For example, you might want to move a volume to a different filer to

• replace the volume's disk shelf with one that has a greater storage capacity
• gain access to the files on a dead filer

When a filer detects a foreign volume at boot time, it places the foreign volume off-line. You can then bring the foreign volume on-line. For more information about installing and bringing up a foreign volume on-line, refer to "Adding a foreign volume."

Copyright © 1999, Network Appliance, Inc. All rights reserved.

Part No. 210-02166
File: disk2.htm
Last updated: 02/24/99 15:46:00