Virtual Tape to Physical Tape Transfer Techniques

DXi contain partitions — or virtual tape libraries (VTLs) — that present the virtual media changer and virtual tape drives to the host exactly as they would to a physical tape library (PTL). This presentation allows the same drivers to be used for both VTLs and PTLs. Existing backup processes are identical, and creating a backup image on a virtual tape is no different from creating a backup image on a physical tape. The backup functionality and data path are unchanged.

Figure 1: VTL Backup Scenario

After the normal DXi backup process has completed, each backup application implements its own technique to transfer stored data from virtual tape to physical tape.

Symantec NetBackup, Symantec Backup Exec, and ASG-Time Navigator

These backup applications can perform a copy operation using Network Data Management Protocol (NDMP) to transfer data directly from the virtual tape library (VTL) to the physical tape library (PTL) over a Fibre Channel connection.

The backup application server controls the copy process, but it does not read or write the data, which in turn frees it to do other tasks. Because this data transfer is a normal duplication job, the physical tape copy is cataloged in the backup application’s database. You can restore data directly from either virtual or physical copy because both the VTL and the PTL are visible to the backup application.

Workflow

To duplicate the virtual tape image, the backup application performs the following steps:

Selects an NDMP device path to the VTL.
Creates an NDMP control session for this device.
Selects a tape volume from the PTL.
Selects an NDMP device path from this library.
Creates a second NDMP control session for this device.
Sends NDMP messages via the control sessions both to move data and to monitor the data transfer.
Writes headers and handles tape spanning and errors, as needed.

Figure 2: Duplicating Virtual Tape Image

EMC Networker

With EMC NetWorker, the DXi can move cloned data directly between its VTL and the PTL. The NetWorker storage node manages the cloning process, while the DXi manages the actual data transfer.

For data transer, the VTL presentation layer supports Fibre Channel connections. A second path, accessible via NDMP via Fibre Channel, supports the enhanced VTL to PTL clone operations with NetWorker.

The PTT feature allows both the VTL and the PTL to be visible to NetWorker, enabling you to restore data directly from either virtual or physical copy. NetWorker automatically catalogs the physical tape barcode in its database.

Workflow

To clone data directly from the VTL to the PTL, NetWorker performs the following steps:

Through the DXi, selects the NDMP device paths (via Fibre Channle) to the VTL and PTL.
Through NDMP, identifies a source and destination for the data movement within the DXi.
Creates another NDMP control session for this device.
Sends NDMP messages via the control session to manage the overall process, as well as to monitor the data transfer taking place at the back end of the DXi appliance.
Updates the headers on the physical tape to manage the new barcodes.

Figure 3: Duplicating Virtual Tape Image

Oracle Secure Backup

Oracle Secure Backup (OSB) can duplicate or migrate virtual tapes to physical tapes on a one-off basis or per user-defined policy.

Duplication

Creates a tape copy with identical backup data but a unique tape ID for tracking purposes. After a duplication operation completes, two copies of the backup data exist.

Migration

Creates an identical tape copy with a unique tape ID, and then deletes the original tape thereby freeing up space on the VTL. After a migration operation completes, one copy of the backup data exists on tape.

Configuring tape duplication or migration can be accomplished using the OSB Web Tool, command line (obtool), or Oracle Enterprise Manager (EM) Grid Control 10.2.0.5.

Workflow

Perform a one-off duplication or migration from the OSB Web Tool:

Open the OSB Web Tool Volumes page.
Figure 4: OSB Web Tool Volumes Page
Select the desired volumes to duplicate or migrate.
Click the Duplicate button to display options for duplicating or migrating the volumes.
Select the appropriate option.