Virtual Tape Library (VTL) configuration in Tivoli Storage Manager TSM

A Virtual Tape Library or VTL, is an backup solution that combines traditional tape backup methodology with low-cost disk technology to create an optimized backup and recovery solution.  It is an intelligent disk-based library that emulates traditional tape devices and tape formats. Acting like a tape library with the performance of modern disk drives, data is deposited onto disk drives just as it would onto a tape library, only faster. Virtual tape backup solutions can be used as a secondary backup stage on the way to tape, or as their own standalone tape library solution. A VTL generally consists of a Virtual Tape appliance or server, and software which emulates traditional tape devices and formats.

Defining a VTL to the Tivoli Storage Manager server can help improve performance because the server handles mount point processing for VTLs differently than real tape libraries. The physical limitations for real tape hardware are not applicable to a VTL, affording options for better scalability.  You can use a VTL for any virtual tape library when the following conditions are true: 

• There is no mixed media involved in the VTL. Only one type and generation of drive and media is emulated in the library. 

• Every server and storage agent with access to the VTL has paths that are defined for all drives in the library.

If either of these conditions are not met, any mount performance advantage from defining a VTL library to the Tivoli Storage Manager server can be reduced or negated.

VTLs are compatible with earlier versions of both library clients and storage agents. The library client or storage agent is not affected by the type of library that is used for storage. If mixed media and path conditions are true for a SCSI library, it can be defined or updated as LIBTYPE=VTL.

You have to define a virtual tape library (VTL) to TSM Server to take advantage of mount performance and scalability advantages. VTLs are identified by using the DEFINE LIBRARY command and specifying LIBTYPE=VTL. Because a VTL library functionally interacts with the server in the same way that a SCSI library does, it is possible to use the UPDATE LIBRARY command to change the library type of a SCSI library that is already defined. You do not have to redefine the library. 

To help prevent out-of-space errors, ensure that any SCSI library that you update to LIBTYPE=VTL is updated with the RELABELSCRATCH parameter set to YES. The RELABELSCRATCH option enables the server to overwrite the label for any volume that is deleted and to return the volume to scratch status in the library. The RELABELSCRATCH parameter defaults to YES for any library defined as a VTL.

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How to add a new VTL to TSM Server 

If you have a new VTL library and want to use the VTL enhancements that are available in Tivoli Storage Manager Version 6.3, define the library as a VTL to the server:

                            define library VTLIB libtype=vtl

This sets up the new VTL library and enables the RELABELSCRATCH option to relabel volumes that have been deleted and returned to scratch status.

How to update an existing SCSI library to a VTL in TSM

If you have a SCSI library and you want to change it to a VTL, use the UPDATE LIBRARY command to change the library type:

                           update library TSMIB libtype=vtl

You can only issue this command when the library being updated is defined with LIBTYPE=SCSI.

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How to revert a real tape library from the VTL library type

If you define a SCSI tape library as a VTL and want to change it back to the SCSI library type, update the library by issuing the UPDATE LIBRARY command:

                              update library VTLLIB libtype=scsi