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[TIGGE #YSF-211129]: TCP tuning for TIGGE tuning



YangXin,

After looking at our AIX systems here, I've not done much if any TCP tuning on 
them.
I did run a fair number of tests since yesterday, and found the default AIX 
values do
siginificantly reduce bandwidth over a long distance, higher latency 
connection.  
Please run the following command "no -a" and check the default values for 
rfc1323, 
tcp_recvspace, tcp_sendspace, sb_max, and sack and make a note of them.  
Our default values were;

 rfc1323 = 0
 tcp_sendspace = 16384
 tcp_recvspace = 16384
 sb_max = 1048576
 sack = 0

after making the following changes, there was a 10-20 times improvement in the
bandwidth (from 1.6Mbps to 20-38Mbps) using "no -a <parameter>=<value>"

 rfc1323 = 1
 tcp_sendspace = 262144
 tcp_recvspace = 262144
 sb_max = 8388608
 sack = 1

I did see modest improvements when setting tcp_sendspace and tcp_recvspace 
higher than 262144, but values above 524288 caused the performance to decrease.

After making these changes, you'll need to restart the LDM or other software
doing data transfers to see the benefit of the changes.  Also, note that these
changes are temporary and will be lost after a system reboot.  There are a
number of ways to make the changes permanent if they work well.  Please see the 
following for more details;

 http://publib16.boulder.ibm.com/pseries/en_US/aixbman/prftungd/netperf3.htm

For additional tuning, we'll need the know the IP address / hostname of your
LDM reception system, and possibly a local account.  Please let us know the
results of these changes on your system.  Best regards,

mike

> The OS for my system is AIX 5L 5.1 with maintenance level 02 (5100-02), it is 
> a node in a RS/6000 SP
> with 2 POWER3 Processors and 1GB of memory. We are planning to implement a 
> new platform to substitute
> for the old SP. The new system will be using Linux as the OS, SUSE or Redhat 
> is the most probable choice.
>
> I intuitively think that Linux is better than AIX to do the business relating 
> to network, such as data
> transfter across networks and servers. However, probably it is only because 
> the default settings for
> Linux is good for network.
> 
> So what settings do you think I can change to improve the network or TCP 
> performance for the current
> system. Is there any difference when tunning the TCP performance between AIX 
> and Linux for LDM?
> 
> There are subtle differences in tuning AIX and Linux (mostly parameter 
> names), but in general,
> the network stacks on most Unix systems have evolved from the same basic model
> 
> Thank you.
>
> YangXin,
> Dec 15.


Ticket Details
===================
Ticket ID: YSF-211129
Department: Support IDD TIGGE
Priority: High
Status: Closed


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