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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
--
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Bryan Wright |"If you take cranberries and stew them like
Physics Department | applesauce, they taste much more like prunes
University of Virginia | than rhubarb does." -- Groucho
Charlottesville, VA 22901|
(434) 924-7218 | bryan@xxxxxxxxxxxx
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