On Thu, Sep 02, 2010 at 11:00:12AM +0200, Bernd Schubert wrote: > On Thursday, September 02, 2010, Andrew Beekhof wrote: > > On Wed, Sep 1, 2010 at 11:59 AM, Bernd Schubert > > > My proposal is to rip out all network code out of pingd and to add > > > slightly modified files from 'iputils'. > > > > Close, but thats not portable. > > Instead use ocf:pacemaker:ping which goes a step further and ditches > > the daemon piece altogether. > > Hmm, we are already using that for now temporarily. But I don't think the > ping > RA is suitable for larger clusters. The ping script RA runs everything > serially and only in intervals when called by lrmd. Now lets assume we have a > 20 node cluster. > > nodes = 20 > timeout = 2 > attempts = 2 > > Makes 80s for a single run with default already rather small timeouts, which > is IMHO a bit large. And with a shell script I don't see a way to improve > that. While we could send the pings in parallel, I have no idea how to lock > the variable of active nodes (active=`expr $active + 1`). I don't think that > the simple sh or even bash have a semaphore or mutex lock. So IMHO, we need a > language that supports that, rewriting the pingd RA is one choice, rewriting > the ping RA into python is another.
how about an fping RA ? active=$(fping -a -i 5 -t 250 -B1 -r1 $host_list 2>/dev/null | wc -l) terminates in about 3 seconds for a hostlist of 100 (on the LAN, 29 of which are alive). > So in fact my first proposal also only was the first step - first add better > network code and then to make it multi-threaded - each ping host gets its own > thread. A working pingd daemon has the additional advantage that it can ask its peers for their ping node count, before actually updating the attribute, which should help with the "dampen race". > Another reason why I don't like the shell RA too much is that shell takes a > considerable amount of CPU time. For a subset of systems where we need ping > as > replacement for quorum policy (*) CPU time is precious. > > Thanks, > Bernd > > PS: (*) As you insist ;) on quorum with n/2 + 1 nodes, we use ping as > replacement. We simply cannot fulfill n/2 + 1, as controller failure takes > down 50% of the systems (virtual machines) and the systems (VMs) of the 2nd > controller are then supposed to take over failed services. I see that n/2 + 1 > is optimal and also required for a few nodes. But if you have a larger set of > system (e.g. minimum 6 with the VM systems I have in my mind) n/2 + 1 is > sufficient, IMHO. You meant to say you consider == n/2 sufficient, instead of > n/2 ? > Therefore I asked before to make the quorum policy > configurable. Now with Lustres multiple-mount-protection and additional stop > of resources due to ping, I'm willing to set quorum policy to ignore. -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. _______________________________________________ Pacemaker mailing list: Pacemaker@oss.clusterlabs.org http://oss.clusterlabs.org/mailman/listinfo/pacemaker Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker
