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Restore processing has changed since then: during the process directories will
be created with default attributes and the correct attributes and ACL information
is applied once the data is read from the media. Therefore the original reason to
cache directories on disk no longer applies.
Nevertheless, the DIRMC option is still useful. If you do not specify this option to
associate a management class with directories, the client, during backup, uses
the management class in the active policy set of your policy domain with the
longest retention period, which could point to a storage pool on tape. This might
result in unwanted mount requests during a backup. Therefore, in the design
described in this book, we have used a separate storage pool and management
class for directories and recommend using the DIRMC option.
QUIET
The QUIET option keeps messages from being written to the screen during
backups. By default, Tivoli Storage Manager displays information about each file
it backs up. To prevent this, use the QUIET option. Messages and summary
information are still written to the log files.
There are two main benefits of using the QUIET option:
For tape backup, the first transaction group of data is always resent. To avoid
this, use the QUIET option to reduce retransmissions at the client.
If you are using the client scheduler to schedule backups, using the QUIET
option dramatically reduces disk I/O overhead to the schedule log and
improves Tivoli Storage Manager throughput.
15.5 System design for performance
In this section we discuss some areas of hardware based design considerations
when setting up a Tivoli Storage Manager server system.
15.5.1 PCI busses
Most pSeries machines have multiple PCI busses. As an example, when backing
up to tape over a LAN it is not desirable to have the network adaptor and the tape
(SCSI, fibre) adaptor on the same bus. Spreading the PCI adapters across
different busses based on predicted usage will provide the most efficient layout.
15.5.2 Tape busses (SCSI, Fibre)
Placing too many tape devices on a bus can cause contention issues. For HVD
SCSI tape devices, no more than two devices should be placed on a single bus.
Chapter 15. Performance considerations
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