Storage Management Operations (Labeling and Mounting)

The internal label on a volume contains a unique name that Backup uses to track and recognize storage media. In the media database, Backup refers to volumes by their volume labels. Backup uses the media database records to determine which volumes are needed for backing up or recovering data.

Every volume belongs to a pool. Each pool has a matching label template associated with it. Volumes are labeled according to the rules of these label templates. Label templates provide a way to consistently name and label volumes so you do not have to track the number of volumes you have used. You can use the preconfigured pools and preconfigured (and associated) label templates that come with the Backup product, or create your own pools, label templates, and pool/template associations. Customizing your own label templates gives you more control over your data storage organization.

When you put a new internal label on a volume or relabel a volume to recycle, any existing data stored on the volume under the previous label is no longer available for recovery.

Backup Criteria for Volume Selection and Mounting

When a scheduled or manual backup occurs, Backup searches for a volume from the appropriate pool to accept the data that needs to be written. The storage volumes available for Backup to use are the volumes that are mounted on standalone devices and the volumes accessible to Backup through auto media management or available to Backup through an autochanger or silo.

If you try to back up files when an appropriate volume is not mounted, Backup requests a writable volume by displaying a message similar to the following in the Pending display:

media waiting: backup to pool `Default' waiting for 1 writable
backup tape or disk

When you start a data recovery, Backup displays a message in the Pending display that requests a mount of the volume name that contains the backed-up data, as in:

media waiting: recover waiting for 8mm 5GB volume-name

If you need more than one volume to recover the files, the Pending display lists all of the volumes in the order they are needed. During the recovery process, Backup requests the volumes it needs, one at a time.

If you mount more than one volume on the storage devices used by Backup, Backup uses the following hierarchy to select a volume on which to write data:

• An already mounted, appendable volume from the appropriate pool

• An already mounted, recyclable volume from the appropriate pool that is not currently in use

• An already mounted, unlabeled volume that is not currently in use and is in a device for which auto media management is enabled

• An appendable volume that is not currently mounted in the device but is from the appropriate pool

• A recyclable volume that is not currently mounted in the device but is from the appropriate pool

How to Label a Volume

A volume label is a unique internal code applied by Backup that initializes the volume for Backup to use and identifies a storage volume as part of a specific pool. To label a volume, follow these steps:

1. Place an unlabeled or recyclable volume in the Backup storage device.

2. Use Backup to label the volume. You can use either the Backup administration program or the nsrmm command.

   There are three options:

   • If you do not select a pool for the volume that you are about to label, Backup automatically applies the label template associated with the Default pool.

   • To create individual label names not associated with a template, edit the Volume Name attribute in the Label resource and enter a unique label name.

   • If you enable the Manual Recycle attribute when you label a volume, the volume cannot automatically be marked as recyclable according to the retention policy. Only an administrator can mark the volume recyclable.

   When Backup labels a volume, Backup first verifies that the volume is unlabeled. Then Backup labels the volume with the name specified in the Volume Name attribute, using either the next sequential label from the label template associated with the chosen pool or an override volume name you entered.

   If you relabel a recyclable volume from the same pool, the volume label name and sequence number remain the same, but access to the original data on the volume is destroyed and the volume becomes available for new data.

   After a volume is labeled and mounted in a device, the volume is available to receive data. Because the Backup label is internal and machine-readable, it is a good idea to put an adhesive label on each volume that matches the internal volume label. To use barcode labels with an autochanger, see "How Backup Uses Barcode Labels with Autochangers". To use barcode labels with a silo, see "Labeling Volumes in a Silo".

How to Mount or Unmount a Volume

When you issue the command to mount a volume or when Backup mounts a volume through auto media management, a volume that is loaded in the storage device is prepared to receive data from Backup. For example, when a tape is mounted, the read/write head of the device is placed at the beginning of the blank part of the tape, ready to write.

To mount the volume in the device, you can use either the Backup administration program or the command line:

• In the Backup administration program, select the device from the Devices display, then click the Mount button.

• At the shell prompt, enter the nsrmm command with the -m option.

After you label and mount a volume, the volume name is displayed in the Devices resource beside the pathname of the device in the Backup administration program.

To perform an unattended backup using a standalone device, you must mount labeled volumes in the device before leaving it unattended.

You can only use nonrewinding devices with Backup. If you use a rewinding device, the read/write head is repositioned at the beginning of the volume and the previously backed-up data is overwritten.

Timeout Settings for Remote Devices

You can time out a mount request on a remote device storage node and redirect the save to another storage node. Set the attributes Save mount timeout and Save lockout in the Devices resource to change the timeout of a save mount request on a remote device. If the mount request is not satisfied by the number of minutes specified by the Save Mount Timeout attribute, the storage node is locked out from receiving saved data for the number of minutes specified by the value of the Save Lockout attribute. The default value for Save mount timeout is 30 minutes. The default value for Save lockout is zero, which means the device in the storage node continues to receive mount requests for the saved data.

The Save mount timeout only applies to the initial volume of a save request.

How to Find a Volume Name

If the adhesive label on the volume is missing or illegible, you can determine the volume's name from the Backup administration program or the command line, complete one of the two actions:

• In the Backup administration program, either

  • Mount the volume and view the volume name in the Devices display, or

  • Start a labeling operation and view the Volume Name field in the Label resource, then cancel the operation.

• At the shell prompt, enter the nsrmm command with the -p option to show the label of the volume loaded in a device.

How Backup Selects a Storage Volume for Relabeling

Backup data is destined for volumes from a specific pool. When the data is ready to be written, Backup monitors the active devices to locate a volume from the appropriate pool.

If only one volume from the pool is mounted and appendable, the data is directed to that volume.

If two volumes from the same pool are mounted on devices, Backup considers the following factors to guide its volume selection:

• The expiration date of the volume

  By default, the volume expiration date is set at two years after the date on which the storage volume was labeled (or relabeled). To override this default setting, change the volume's expiration date in the Devices resource. If the default setting is overridden, Backup checks to ensure that the volume expiration date is farther in the future than the date on which the save set is set to exceed its retention policy. If Backup finds that the volume expiration date is later than the retention policy, then the save set is written to the volume. Otherwise, Backup does not write the save set to the volume. (This checking behavior does not occur if the expiration date of the volume is not overridden.)

• The volume mode

  • If a mounted, appendable volume from the appropriate pool is available, Backup writes to it.

  • If there is no appendable volume of the appropriate pool available (and if you enabled auto media management), Backup recycles and then writes to a mounted, recyclable volume from the appropriate pool as a second choice. (Backup does not consider writing to a mounted, recyclable volume that belongs to a different pool.)

  • If no volumes of the pool are available (and if you did not enable auto media management), Backup labels, mounts, and writes to a new, unlabeled volume or a volume that does not have a Backup label.

• The volume label time, which is the time when the volume was labeled

  Volumes with the oldest label time are selected before volumes that were labeled more recently.

• The number of sessions currently writing to the device

If Backup cannot find a mounted volume from the appropriate pool, a mount request is initiated. If auto media management is not enabled or if Backup has only standalone devices available, mount requests continue to be generated until a volume is mounted and backup can begin.

Auto Media Management

The auto media management feature gives Backup automatic control over media loaded in the storage device. If you enable the auto media management feature in the Devices resource, Backup automatically labels, mounts, and overwrites a volume it considers unlabeled, and automatically recycles volumes eligible for reuse that are loaded into the device. The auto media management feature is only enabled for standalone devices in the Devices resource. To enable auto media management for devices in an autochanger, see "Auto Media Management With Autochanger Devices".

Backup considers a volume unlabeled in the following conditions:

• The volume has no internal label.

• The volume is labeled with information other than a recognizable Backup label.

• The volume is labeled with a Backup label, but the density indicated on the internal label differs from the density of the device where the volume is mounted.

Because the auto media management feature can relabel a volume with a different density, it is possible to inadvertently overwrite data that still has value. For this reason, be careful if Backup volumes are shared between devices with different densities.

If you do not enable the auto media management feature, Backup ignores unlabeled media and does not consider it for backup.

If you enable the auto media management feature for a standalone device, Backup exhibits the following behavior when a volume becomes full during a backup:

1. Backup issues a notification that it is waiting for a writable volume. At the same time, Backup waits for the full, verified volume to be unmounted.

2. Backup monitors the device and waits for another volume to be inserted into the device.

3. After a volume is detected, Backup checks that the volume is labeled. If so, Backup mounts the volume. Backup checks to see whether the volume is a candidate to write data to. If so, the write operation continues. If not, Backup continues to wait for a writable volume to continue the backup.

4. If the volume is recyclable and is a member of the required pool, Backup recycles it the next time a writable volume is needed.

5. If the volume is unlabeled, Backup labels it when the next writable volume is needed for a save.

In general if a non-full volume is unmounted from a standalone drive and you enabled auto media management, Backup waits for 60 minutes before it automatically remounts the volume in the drive. This hour is considered a reasonable delay to give you or an operator time to unload the volume after unmounting.

Backup considers volumes that were labeled by a different application to be a valid relabel candidate if automedia management is enabled. Once Backup relabels the volume, the previously stored data is lost.