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Gigabit technology supports jumbo frames (9000 bytes), which should be used
whenever Gigabit Ethernet hardware is implemented. Unfortunately not every
Gigabit hardware component implements jumbo frames. Using this feature is
only practical when all elements (server, switch, and client) are capable of it.
15.5.6 Tape devices
Calculation of your daily throughput for backup and archive data as well as the
amount of data being sent directly to tape should lead to a minimum number of
tapes that should be in place to sustain your data flow. Remember to size the
number of tape devices to serve the data flow during the
not on an daily average basis.
If you have to schedule certain server operations like migration, reclamation, or
storage pool backup during the backup window, make sure that there are enough
tape drives available to support these additional operations. Even if these server
operations are typically scheduled outside the normal backup window, you
should allow a number of tape drives serving unscheduled restore or retrieve
operations.
15.6 Special performance tips
This section describes tuning tips for special areas that may depend on a certain
operating system.
15.6.1 LAN-free tuning
When using LAN-free backup and restore, TCPNODELAY must be set to YES
(the default) on the Storage Agent and server.
15.6.2 LTO/DLT tape tuning
Due to the high latency of the write filemarks command, LTO and DLT tape
devices benefit from making Tivoli Storage Manager transactions as large as
possible. Setting server TXNGROUPMAX to greater than 512 files and client
TXNBYTELIMIT to the maximum of 2097152 bytes can reduce the number of
transactions, enhancing performance. It is important to understand that these
settings can effect the server's recovery log utilization, and will increase the
amount of time between transaction commits. At Tivoli Storage Manager V5.2
and later, the maximum setting for the TXNGROUPMAX value has been
increased from 256 to 65000. The double-up and test rule should be followed for
these parameters.
peak
Chapter 15. Performance considerations
backup window,
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