STORE and TurboSTORE/iX Products Manual (B5151-90003)

Chapter 6 113
STORE and TurboSTORE/iX Command Options
TurboSTORE/iX II Options
TurboSTORE/iX II Options
The following options are available only if the TurboSTORE/iX II product is purchased.
In addition to all of the STORE options, the following additional options are available with
TurboSTORE/iX II. For more information on purchasing TurboSTORE/iX II, contact your
Hewlett-Packard sales representative.
COMPRESS For file compression
Compressing Data (COMPRESS)
With TurboSTORE/iX II (and TurboSTORE/iX 7x24 True-Online Backup), backup
performance can be improved through the use of host data compression. By specifying the
COMPRESS parameter, the host system filters the data through a compression algorithm
prior to writing it to the backup device. This operation has two effects:
• The device's throughput is increased by transferring more data than the device's
maximum sustained rate. The increase is dependent upon available CPU resources.
• Fewer media changes are required by putting more data on each piece of media.
Two levels of compression are supported by the COMPRESS parameter: HIGH and LOW.
NOTE No matter whether you specify HIGH or LOW, the actual level of data
compression is dependent upon the type of data being compressed. For
example, program files will not compress as much as data files.
You must determine which of the compression algorithms best suits your needs. In some
cases the low-compression algorithm may perform almost as well as, or better than, the
high-compression algorithm.
It is advisable to try both algorithms on your data in order to evaluate which algorithm
best suits your needs. Some of the factors to consider are:
• Elapsed time of backup.
• Amount of CPU time required.
• Amount of media required.
Be advised that when performing backups with the high-compression algorithm, the
backup can consume much or most of the processing capabilities of the machine. The exact
amount of system resources consumed depends on your system speed and multi-processor
configuration. Using the low-compression algorithm demands less system resources, so it
is easier for other activity to coexist with the backup.
Use the high-compression algorithm if backup time is dedicated or if the difference in the
amount of media used for backup is substantial enough to warrant the complete
consumption of the machine.
When compressed format files are restored, RESTORE automatically recognizes the
compressed format and restores the files properly.