NetVault 11.4.5 - Administration Guide

About Virtual Tape Library

Virtual Tape Libraries (VTLs) emulate tape libraries on disk. VTLs are included in NetVault Backup as a licensable option.

With VTLs, you have the flexibility to perform quick backups to disks, and during off-peak hours migrate or duplicate the backups to physical devices for off-site storage. The Media Manager does not distinguish between virtual and physical tapes. Therefore, you can use the same process to set up backup policies, including retirement period and rotation schemes.

VTLs are represented as directories on the disk. Each VTL contains three directories: drives, slots, and media. These directories contain numbered subdirectories. The virtual drives reside as files in the drives subdirectories. These files contain links to the media files. The virtual tapes reside as media files in the media directory. When a virtual tape is moved between slot and drive, the media file itself stays in the media directory, while the drives and slots files are modified to emulate the moving of the media.

A VTL can handle any number of concurrent NetVault Backup Client backups. As with a physical library, the number of drives contained in the VTL dictate how many simultaneous operations can be performed. The number of slots should be the same as or more than the number of configured drives. Different operating systems may impose maximum file-size limits, which can affect the maximum VTL media size.


	NOTE: VTLs are independent of file systems (for example, NTFS, UFS, ext3, and others) and disk systems (for example, IDE, SCSI, iSCSI, and others), but VTLs do not support file systems residing on removable drives.

Virtual Tape Library considerations

Before creating and adding a VTL, review the following information:

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Before creating a VTL, NetVault Backup performs a disk space check to ensure that the target disk has sufficient space to accommodate the new VTL.

On normal file systems you can use the disk space check feature to avoid errors during VTL creation. When creating a VTL on a third-party deduplication appliance or compressed file system, you should disable this feature. For more information, see Configuring default settings for Disk Devices Plug‑in.

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During disk space checks the free space required on the disk is calculated as follows:

Number of Slots * Media Capacity + <x>

Here <x> is the additional disk space considered for the following requirements:

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Disk space required to create the directory structure for VTL. The requirement varies for different file systems.

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Disk space required by other applications running on the system.

By default, the additional space requirement is set to 20MB. To change this setting, see Configuring default settings for Disk Devices Plug‑in.

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If the target disk does not have sufficient space to accommodate the specified VTL, the device emulation process is terminated and a message is displayed.

Creating and adding a Virtual Tape Library

You can use the configuration wizard to create a virtual tape library on the NetVault Backup Server or a SmartClient. When creating a VTL, you can choose the number of virtual tape drives and slots, and specify the size of the virtual tapes. After the device is created, it is automatically added to the server.

To create and add a Virtual Tape Library:

In the Navigation pane, click Guided Configuration, and then on the NetVault Configuration Wizard page, click Add Storage Devices.

— or —

In the Navigation pane, click Manage Devices, and then click Add Device.

On the Add Storage Devices page, select the Virtual tape library/media changer option, and click Next.

In the list of NetVault Backup machines, select the machine on which you want to create the device, and click Next.

On the Add Virtual Tape Library page, provide the following details.

Figure 10. Add Virtual Tape Library page

Table 18. Add Virtual Tape Library


Option	Description
Choose the location on disk where you wish to create the new device	Specify the location where you want to create the VTL. Make sure that the path is already created on the selected machine. NetVault Backup does not create any non-existing directories in the path.
Choose a name for the device	Specify a unique name for the device.
Device display name	Specify a display name for the device.
Choose a 5 character media barcode prefix	The NetVault Backup Server automatically generates a barcode prefix and assigns it to the VTL media. If you want to change it, type a unique code for the device.
Specify the media capacity	Type or select the size of the virtual tape. The media size is specified in GiB. Each slot contains a piece of media of the given size. The default value is 32GiB.
Choose number of drives	Type or select the number of drives for the VTL. You can create maximum of 100 drives. The default value is two drives.
Choose number of slots	Type or select the total number of slots that hold the media. You can specify a maximum of 999 slots. The default value is 16 slots.

Click Next to create and add the device.


	NOTE: The amount of time it takes to create a VTL depends on the media capacity and number of slots specified for the VTL. The time required is proportional to the VTL size.