IBM E16RMLL-I Implementation Guide - Page 543
Special performance tips
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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 peak backup window, 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. Chapter 15. Performance considerations 513
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