Managing virtual libraries
VTL supports two types of compression:
■Hardware compression ‐ uses a Hifn Express DR1000 (1 GB/sec compression) or DR600 (600 MB/sec) compression card. A license keycode is required for hardware compression.
■Software compression ‐ uses an LZO algorithm that runs on the VTL server.
In order to use compression, you must also enable tape drive compression in your backup application.
Note – Note: If you are already using software compression that is supplied by your backup application, you should not use VTL’s compression. Using both types of compression will cause VTL to try to compress already‐compressed data and this can slow down your backups.
▼To enable or disable compression:
1.Enable tape drive compression in your backup application.
2.If you are using hardware compression, install a certified compression card in your VTL server.
You can have up to two compression cards per VTL server.
The compression card(s) must be installed before compression begins. If you try to use hardware compression and a compression card is not available, VTL will send an error message to the console event log and uncompressed data will be written to the virtual tape drive.
3.In the VTL Console, right‐click on VirtualTape Library System and select Properties.
4.Select the Enable VirtualTape Library compression mode checkbox and specifywhether you are using Software or Hardware compression.
If you are upgrading a VTL system that previously used software compression to now use hardware compression, the compression mode will be switched to hardware when the tape is overwritten.
Both types of compression are global settings, which means that they will apply to all tapes in your system.
If compression is enabled on the VTL server, you can still disable or enable compression on each individual virtual tape drive in the same manner as real tape drives ‐‐ via your backup application or via SCSI commands which are sent by the operating system.
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