IBM System Storage TS7600 ProtecTIER Series, Installation Roadmap Manual

Page: 214 / 232

v The Mbits/sec reported in this test is the maximum replication performance
your system may achieve. If this number is lower than anticipated, contact your
network administrator.
Test 6: TCP Retransmissions vs. Total TCP segments sent
Example result:
Number of TCP segments sent: 1619061
Number of TCP retransmissions detected: 201038 (12%)
Interpreting the results:
v A total of 1619061 TCP segments were sent during the five tests, out of which,
201038 were lost and retransmitted.
v
The retransmission rate imposes a direct penalty on the throughput, as the
retransmission of these packets take up bandwidth. The retransmission can be
caused by the underlying network (e.g. packet dropping by an overflowed
router) or by the TCP layer itself (e.g. retransmission due to packet reordering).
v Segment loss can be caused by each of the network layers.
v
TCP retransmission larger than 2% may cause performance degradation and
unstable network connectivity. Contact your network administrator to resolve
this issue and reduce it to approximately 0%.
What to do next
You may want to run these tests again to test the reverse throughput in the
network. To run the tests in reverse, change server1 to the client and server2 to the
server and repeat the procedures.
176
IBM System Storage TS7600 with ProtecTIER: Installation Roadmap Guide