[lvs-users] Slow IPVS performance under Centos 6.5

[Michael Schwartzkopff]

Am Freitag, 23. Mai 2014, 10:44:10 schrieb Bryan K. Wright:
> Hi folks,
> 
> 	I've been successfully using IPVS under CentOS 5 for a long
> time, and I've recently been using it with CentOS 6.  Just this
> week I noticed a performance problem with the CentOS 6 cluster, though,
> and I'm wondering if anyone can offer advice on how to track it down.
> 
> 	In both cases, the IPVS setup directs incoming ssh connections
> to one of several login nodes, something like this:
> 
> TCP  my.host.edu:ssh wlc
>   -> host1.internal:ssh            Masq    9      0          0
>   -> host2.internal:ssh            Masq    10     0          0
>   -> host3.internal:ssh            Masq    10     0          0
> 
> On the CentOS 6 cluster, I noticed that X applications like emacs
> were taking a long time to open, and were very laggy.  The CentOS 5
> cluster doesn't act this way at all.
> 
> 	I did some experiments, and I find that if I bypass IPVS and
> ssh to the CentOS 6 director machine, and then ssh from there to one
> of the internal hosts, X applications are as fast as the CentOS 5
> cluster through IPVS.
> 
> 	I also tried manually setting up a DNAT forwarding rule
> on the CentOS 6 director machine, like this:
> 
> iptables -A PREROUTING -t nat -p tcp -d my.host.edu --dport 2201 -j DNAT
> --to host1.internal:22
> iptables -I FORWARD -p tcp -s -d host1.internal --dport 22 -j ACCEPT
> 
> If I then ssh to my.host.edu:2201 (ending up on host1.internal),
> X applications are as fast as on CentOS 5 through IPVS.
> 
> 	Any suggestions on how I can debug this?  The IPVS configurations
> on the two clusters are identical.  What should I be looking at?
> 
> 	Thanks in advance for any advice.
> 
> 						Bryan

I saw this problem, if the tcp checksum calculation was done on the interface. 
Please use ethtool to switch tcp-checksum off in the IF driver.

-- 
Dr. Michael Schwartzkopff
Guardinistr. 63
81375 München

Tel: (0162) 1650044
Fax: (089) 620 304 13
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