Hi, On Mon, May 04, 2009 at 11:37:42AM +0200, Peter Kruse wrote: > Hi Dejan, > > Dejan Muhamedagic wrote: >> As usual, constructive criticism/suggestions/etc are welcome. > > Thanks for sharing. > Allow me to bring up a topic that to my point of view is important. > You have written: > >> The lights-out devices (IBM RSA, HP iLO, Dell DRAC) are becoming >> increasingly popular >> and in future they may even become standard equipment of of-the-shelf >> computers. >> They are, however, inferior to UPS devices, because they share a power >> supply with their >> host (a cluster node). If a node stays without power, the device supposed to >> control it >> would be just as useless. Even though this is obvious to us, the cluster >> manager is not >> in the know and will try to fence the node in vain. This will continue >> forever because all >> other resource operations would wait for the fencing/stonith operation to >> succeed. > > This is the same problem with PDUs as they share the same power supply with > the host as well.
Never worked with PDUs, but there should be a difference compared to the lights-out devices: if a PDU looses power then all nodes connected to it do as well. I suppose that that is much more likely than only one outlet failing. In that case all cluster is down and you have other things to worry about rather than fencing. > Is there any intention to deal with this issue? I'm > thinking of the powerfail algorithm: > > If the PDUs becomes unavailable and shortly after the host is unavailable as > well, then assume the host is down and fenced successfully. > > This would be true if the PDU (and with it the host) loses power. > At the moment it looks that stonith without such an algorithm is > a SPoF by design, because after a single failure (powerloss), the > cluster is not able to bring up the resources again. This is something certainly worth looking at. On the other side, it's not really so difficult or pricey to devise a setup where you won't have to worry about this detail. Cheers, Dejan > Looking forward to your comments, > > Peter > > _______________________________________________ > Pacemaker mailing list > Pacemaker@oss.clusterlabs.org > http://oss.clusterlabs.org/mailman/listinfo/pacemaker _______________________________________________ Pacemaker mailing list Pacemaker@oss.clusterlabs.org http://oss.clusterlabs.org/mailman/listinfo/pacemaker
