Sun Microsystems Virtual Tape Library - Manual (Page 99)

Managing virtual libraries
96267 • G Chapter 4 VTL operations 85
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.