Hello, Am 04.03.2010 um 17:24 Uhr schrieb Josip Rodin <joy@debbugs.entuzijast.net>: > On Thu, Mar 04, 2010 at 05:21:31PM +0100, Markus Hochholdinger wrote: > > > In my case this manifested itself when some PHP profiling via > > > microtime() suddenly became useless, and it also caused occasional > > > PostgreSQL errors with tables that had timestamp columns as keys, since > > > it became possible for two independent transactions to come in at the > > > exact same time. > > have you any service like ntp running on these boxes!? What will the app > > do if ntp "corrects" the time!? > NTP always corrects time in a very subtle manner (see its documentation). > I guess it's possible for it to screw with this, yet it never has. for me, i try to only run ntp on the dom0 and no ntp on the domus. I never had a problem with this running 2.6.18 as dom0 and i never had a problem with this running 2.6.26 as dom0. With older xen kernels (i believe it was 2.6.16) i had a problem that the domU clock went wrong while the dom0 clock was correct, so at this time i changed independent_wallclock to 1 and setup ntp in the domU. Some of this domUs run till today with independent_wallclock 1 and ntp inside the domU without problems. Another note about stability: Since linux-image-2.6-xen-686 (2.6.26-20, october 2009) my dom0s with the lenny dom0 kernel are stable and had no crashes (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=542250). Now i try to use this kernel as domU kernel, but till now (2.6.26-22) it isn't stable enough for me, see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=534880 . Also some combination of java, debian 3.1 and kernel doesn't work with 2.6.26. java segfaults, but only when started with 2.6.26 and not when startet with 2.6.18. Also the same java version on older or newer debian system works. So for now i will use 2.6.18 (redhat xen flavor) for my domUs. Also linux-image-2.6.32-4-686 seems very good as domU, but i only made a short test: live migration works, mem-set works and detach and attach of a block device works as expected. -- greetings eMHa
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