Back with more testing. So because FTB Flux 0.7.1 is officially available, i did a clean install on a second windows pc for server and a clear client installation on my main pc and i did no mods updates. No new Chisel, Facades or even Buildcraft. I just used the mods within the server/client.zip.
What should i say..... lag is gone. So i tried the same with my Linux pc but there the lag is still noticeable. Maybe because of Linux, maybe because of OpenJDK.... who knows.
The funny thing is, my 2nd win pc is older than the linux pc (Core2Quad Q9450 @2,66GHz) and i played a HQ Youtube Video besides running the server..... its a weird world
So now the task is finding out why server on linux pc running not smooth anymore. Just to remember, back in version 0.5.8 it runs perfect.
EDIT: 21.15 GMT.... sigh, crash with either RefinedRelocation, Betterbarrels, LogisticsPipes or all of them, when im far away from home base... trying to update manually to newer versions (if exist).
EDIT2: Updated RefinedRelocation to 1.0.6h helped. No crash since an hour.