Dell NetWorker 19.9 Administration Guide

Device requirements

NetWorker requires two or more storage devices to perform a clone operation. One device contains the volume with the original data and one device contains the volume to which NetWorker writes the clone data. The clone data must reside on a volume that differs from the original volume. Each clone volume can only contain one instance of a cloned save set, even if the clone operation did not complete successfully. For example, if you want to create three clone copies of a save set, NetWorker must write each clone save set to a separate volume. As a result, you would need three separate volumes.

When using a tape library with multiple devices, the NetWorker Server automatically mounts the volumes that are required to complete the clone operation. When you use standalone tape devices, you must manually mount the volumes. A message in the Alert tab of the Monitoring window indicates which volumes to mount.

Often businesses choose devices for the initial backup that is based on speed or cost requirements. NetWorker supports cloning or staging data to a device type that differs from the source data volume. A common cloning or staging scenario includes using an AFTD for the initial backup to gain speed and versatility benefits, then to clone or stage the data to tape devices or dedpulication devices. This scenario allows for an extended retention period without increasing disk space requirements. The use of deduplication can also provide efficient use of storage. Cloning to or from deduplication devices can ensure that these devices are used effectively. If the clone operation includes save sets from different devices, and you want all the save sets to be written to the same volume, include only one volume in the clone target pool.

Cloning multiplexed backups

You can clone multiplexed save sets. NetWorker writes the clone copies of multiplexed save sets as a single contiguous data stream on the target media (demultiplexed). When you recover from a multiplexed save set, read and recovery times increase as a result of the time NetWorker spends reading and locating the data. The process of demultiplexing save sets by the clone operation allowed you to read and recover data faster from a clone save set than a backup save set.

When you clone multiplex save sets, you can only clone one save set to the same target volume simultaneously. However, if the save sets have separate target volumes, you can start multiple clone sessions simultaneously from the same source.

Save set spanning

Some devices, for example Data Domain, support save set spanning across multiple volumes. When NetWorker clones a save set, the clone copy might start on one volume but continue on one or more additional volumes.

When using devices that support save set spanning, ensure that you:

• Identify save sets that span multiple volumes.
• Keep the number of continued save sets to a minimum.
• Use separate pools and larger or alternative devices.
• Use the Data Domain backup-to-disk and optimized cloning feature with Data Domain devices.
• Plan ahead to ensure that the volumes are available and that they are read in the best sequence.

Save set status

NetWorker does not clone save sets that are recyclable or eligible for recycling. If NetWorker encounters a save set that is not browseable, the save set is skipped and is not cloned. However, the clone status is successful.

Recovery scenarios

When you clone data, you provide the datazone with an alternative data recovery source, which helps to protect against media loss or corruption. However, if the media is located in one of the following locations, then the second copy of the data is still vulnerable to major disasters that can affect the entire site:

• On the same tape library as the original data volume.
• On a deduplication device within the same data center, in a Data Domain environment.
• In an onsite safe.

Sometimes, you may require more copies of a save set to ensure that all the recovery scenarios are accommodated while maintaining the expected return on investment. This requirement may not apply to all clients and all data, or be practical. However, consider the reasons for cloning to ensure that the cloning strategy meets requirements and expectations.

Changing the target device, or moving tapes to a second location after the cloning operation completes, can provide additional protection.

Retention considerations

A Retention policy value applies to every type of save set. The retention policy value determines the length of time that the data remains available for recovery in the NetWorker media database and the client file index. You can specify a retention policy value for the clone save set that differs from the value that is defined for the original save set. When the retention policy differs for the original and clone save set, you can expire the original save set and reclaim the space on the source volume but maintain the data on a clone volume for future recoveries.