High CPU on CSS11503 , with one Flow

Question

Hi,
I've seen some high CPU Utilisation on 2 CSS.
I've figured out, that this Utilisation was created, by a mirroring Task from a database Server.
There was one TCP Connection between 2 Servers, whitch transfered about 60 Mbit/s.
But i saw a CPU-Utilisation from about 30-40% on my SCM which passed the Traffic.
That is some thing i do not understand, because the Forwading of this Flow shoud be done in the Flow-Processor, and the CPU Utilisation which is monitored, is the Session Processor.
The Protocol was TCP 1500, which is Used by Tivoli Storage Manager.
Anybody has some Idea, how this makes so much CPU Utilisation?
The Transfer was about 4 hours, and the CPU Utilisation also.
Best regards
Sven

Answer 1

Hello Gilles,
may i try to show you the network design
<-> <-> <-> css <->
So the traffic was hitting 2 css.
One 11506 with 7.50 103
One 11503 with 7.50.103
The traffic was one TCP Connection between Server1 and Server2 (TCP 1500).
There are no ACL and the traffic was not hitting a content rule.
The 11506 handels normal about 30 mbit/s out, and 10 mbit/s in. Average CPU is about 1% over a day.
The 11053 handles normaly about 5mit/ out and 1 mbit/s in. Average CPU is about 4% over a day.
CPU was about 30% higher on both css, during the replicarton (~3 hours)
I did not took any debug or show commands, because i saw it on my mrtg a day later.
Also, the high cpu was only seen on the SCM Module, the second Module (IOM) was normal.
Best regads
Sven