Tape Utilization

[AQasir]

I have an EML tape library with 4 LTO2 Tape Drives all assigned to a single media server. I am trying to get NetBackup to use old tapes so that I can fill them up to the rim instead of leaving most of them with a lot of space.

I am able to get a backup initiated to a old tape but when the tape fills up...netbackup requests for a new scratch tape instead of using the next tape with some amount of data on it. I know that I have other tapes in the library that are of the same policy type, are owned by the same media server...etc.

So basically here is what I am talking about:

TAPE1 - Has 50 GB left on it.

TAPE2 - Has 50 GB left on it.

TAPE3 - Blank/Scratch tape.

Tape 1 is requested during the next backup and once that fills up I am expecting the backup policy to pick up tape2 but instead netbackup uses tape3. Why ? Can I control this in any way?

Secondly, an associate of mine told me that the mount count is an important number and that when ever I insert new tapes I should change the mount count to a high number so that netbackup logic uses low numbers before high numbers. Is this accurate? Can someone provide greater details to this?

[Rakesh_Khandelw]

An old but still very useful document to provide clearity around how NetBackup selects media -

http://support.veritas.com/docs/229632

ow NetBackup Selects Media in a Robot
When NetBackup automatically selects a volume in a robot, it proceeds as follows:

1. NetBackup searches the NetBackup media catalog for a volume that is already mounted in a drive and meets the following criteria:

Configured to contain backups at the retention level required by the schedule (unless ALLOW_MULTIPLE_RETENTIONS_PER_MEDIA is present in the registry).

In the volume pool required by the backup being performed.

Not in a FULL, FROZEN, IMPORTED, or SUSPENDED state.

Of the same density required by the requested backup and, in the case of a robotic storage unit, in the robot requested by the backup.

Not currently in use by another backup or restore.

Not written in a protected format (see "Allow Media Overwrite" on page 482). This is detected after the volume is mounted. If the volume is in a protected format, it is unmounted and NetBackup resumes the search.

2. If NetBackup cannot find a mounted volume that satisfies the above conditions, it checks its media catalog for any volume that is suitable.

3. If the media catalog does not have a suitable volume, NetBackup searches the volume catalog for one that meets all of the following criteria:

Is the correct media type

Is for the correct robot type (if applicable)

Is located in the requested robotic peripheral (if applicable)

Resides on the requested host

Is in the correct volume pool

Is not currently assigned (not already allocated to NetBackup)

Is not expired (if an expiration date is defined in Media Manager)

Has not exceeded the maximum number of mounts allowed

4. If more than one volume qualifies, NetBackup chooses the one with the least mounts. NetBackup then adds it to the media catalog and assigns it the specified retention level.

5. If there are no un-assigned volumes of the requested type, the backup is terminated with an error indicating no available media.

Media Selection Using Standalone Drive Extensions
When the standalone-drive extensions features is enabled, NetBackup tries to use whatever labeled or unlabeled media happens to be in a standalone drive. This capability is enabled by default during installation. The selection process is as follows:

1. If a backup is requested and an appropriate standalone drive does not contain a volume, NetBackup selects one in the same way as for drives in a robot (see "How NetBackup Selects Media in a Robot" above).

The Device Monitor shows the mount request and an operator must manually insert the volume and assign it to a drive.

2. If an appropriate drive contains a volume, NetBackup tries to select and use the volume that is in the drive.
A volume that has been previously used for backup must:

Not be FULL, FROZEN, or SUSPENDED

Be at the same retention level and in the same volume pool as the backup being performed, unless ALLOW_MULTIPLE_RETENTIONS_PER_MEDIA is included in the registry.

Previously unused media are used by NetBackup.

If the unused media is unlabeled, it can be labeled ahead of time by using the bplabel command. When using this command, specify the -u parameter in order to force assignment of a specific drive index. This eliminates the need to manually assign the drive.

If the media is unlabeled:

NetBackup labels the media

Media Manager adds a media ID to the volume configuration, if necessary. If a media ID is added, the NetBackup registry entry

MEDIA_ID_PREFIX is used as the first characters of the media ID. If MEDIA_ID_PREFIX is not specified, the default prefix is "A". (Example, A00000.)

Media Manager adds the requested volume pool to the volume configuration (if the backup class specifies a volume pool).

Variations of this same information may be found in the Sys Admin guide Vol II under Referece Topics.

[AQasir]

Rakesh,

Thanks for the detailed response. Its exactly what I was looking for !!

I do have one more questions. In reference to step # 4 in your post...Is there any way for me to change how netbackup chooses the tape with the lease mounts to selecting a tape with the most mounts ?