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Further Information
Performance Considerations
Appendix A A-11
NOTE By default, software compression should be disabled. Software
compression should only be used for backup of many systems over a slow
network where the data can be compressed before sending it over the
network. If software compression is used, hardware compression should
be disabled since trying to compress data twice actually expands the
data.
Hardware Compression
Hardware compression is done by a device, which receives the original
data from the Media Agent client and writes it to the tape in compressed
mode. Hardware compression increases the speed at which a tape drive
can receive data, because less data is written to the tape.
By default, hardware compression should be enabled. On HP-UX and
Solaris, hardware compression should be enabled by selecting a
hardware compression device file. On Windows NT and Windows 2000,
hardware compression can be selected during the device configuration.
Using hardware compression or not should be a conscious decision,
because media written in compressed mode cannot be read using the
device in uncompressed mode and vice-versa.
Limitations HP Ultrium LTO drives use automatic hardware compression which
cannot be disabled. Ensure that you do not enable Software
compression when you configure an HP Ultrium LTO drive.
Full and Incremental Backups
A basic approach to improve performance is to reduce the amount of
backed-up data. Take full advantage of time and resources when
planning your full and incremental backups. An important consideration
is that there is no need to do full backups of all the systems on the same
day, unless necessary. See the HP OpenView Storage Data Protector
Concepts Guide for more information.