6.3 Using Virtual Tape Library (VTL) in TSM Environment

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.

With a virtual tape library (VTL), data can either remain in the virtual tape library as long as there is enough space, or it can migrate to tape for off-site storage, or both. It uses a unique blend of several storage tiers. In addition, it has a combination of high-performance SAN-attached disk and high-performance servers that run Linux, emulating a tape storage device.

VTLs maintain volume space allocation after Tivoli Storage Manager deletes a volume and returns it to a scratch state. The VTL keeps the full size of the volume allocated. This allocation might be large, depending on the devices being emulated. As a result of multiple volumes that revert to scratch, the VTL can maintain their allocation size and run out of storage space.

Also Read: Different types of libraries supported by IBM Spectrum Protect (TSM)

The only way for the VTL to realize that a volume is deleted and its space can be reallocated is to write to the beginning of the newly returned scratch volume. The VTL then sees the volume as available. Tivoli Storage Manager can relabel volumes that are returned to scratch if the RELABELSCRATCH parameter is specified.

A virtual tape library (VTL) provides high-performance backup and restore by using disk arrays and virtualization software. A VTL can provide the following benefits
  • Helps to validate data recoverability.
  • Reduces the resources that managing tape media requires.
  • Improves backup and recovery and simplifies disaster recovery operations
  • Lowers operational costs and energy usage.
  • Manages more data with less infrastructure.
Defining a virtual tape library (VTL)
Defining a VTL library includes the following parameters:

Virtual Tape Library (VTL) in TSM

LIBType=VTL (Required): Specifies that the library has a SCSI-controlled media changer device that is represented by a virtual tape library.

SHAREd: Specifies whether this library is shared with other Tivoli Storage Manager servers in a storage area network (SAN).

Also Read: 15 tips to efficiently use the tape drive resources

RESETDrives: Specifies whether the server preempts a drive reservation with persistent reserve when the server restarts or when a library client or storage agent re-connection is established. If persistent reserve is not supported, the server performs a target reset.
  • Yes: Specifies that drive preemption through persistent reserve and target reset are performed. YES is the default for a library that is defined with SHARED=YES.
  • No: Specifies that drive preemption through persistent reserve and target reset are not performed. NO is the default for a library that is defined with SHARED=NO.
AUTOLabel: Specifies whether the server attempts to automatically label tape volumes. This parameter is optional. The default is NO. To use this option, you need to check in the tapes with CHECKLABEL=BARCODE on the CHECKIN LIBVOLUME command.

RELABELSCRatch: Specifies whether the server relabels volumes that are deleted and returned to scratch. When this parameter is set to YES, a LABEL LIBVOLUME operation is started and the existing volume label is overwritten.

SERial: Specifies the serial number for the defined library. This parameter is optional. The default is AUTODETECT. If SERIAL=AUTODETECT, when you define the path to the library, use the serial number that the library detects as the serial number. If SERIAL=serial_number, the number that you enter is compared to the number that Tivoli Storage Manager detects.

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