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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