On Thu, Jan 12, 2012 at 5:58 AM, Dejan Muhamedagic <dejan@xxxxxxx> wrote: > Hi, > > On Wed, Jan 11, 2012 at 01:08:56PM -0500, David Teigland wrote: >> On Wed, Jan 11, 2012 at 11:21:59AM -0500, David Teigland wrote: >> > > I much prefer the expected_votes field to any enumeration of the nodes. >> > >> > Expect admins to keep track of what expected_votes should be? >> > That sounds nearly impossible to do correctly. >> > >> > > Does anyone need the list of nodes to be preconfigured? >> > >> > The alternative would be trying to remember what they all are? >> > Defining the set of nodes that compose the cluster seems like >> > a very good thing just for its own sake. >> >> I guess that's just one view. There really are two legitimate styles >> of assembling a cluster that we're trying to merge. >> >> In the first, you have a conceptual view of just a big pool nodes, more >> or less anonymous. They are just "workers", which higher level software >> (e.g. pacemaker) can use as needed to run things. >> >> The second is a more fixed, static approach. You start with with some >> specific nodes and you want to access some shared resource from those >> nodes. Because the resource is shared, there needs to be clustering >> involved to access it. e.g. this node needs to mount that gfs2 file >> system. >> >> The first view has historically been taken by corosync and pacemaker, >> and the second by cman/gfs2. Folks with the first view would think >> of a static node list as unnecessary, whereas it's the starting point >> in the second view. > > Not sure if I can recall exactly, but HPC clusters belong to the > first category. At least I'd expect them to. > > Even though corosync doesn't require (for multicast) a fixed list > of nodes, I'd put it also in the second category. I doubt that > there are many corosync or openais clusters which have node sets > frequently changing. As for pacemaker, it just gets the > membership events and creates nodes as necessary. Heartbeat > requires that all nodes are listed in static configuration files. No it doesn't. Thats just one mode of operation, it also supports autojoin. > > As for whether admins can err counting nodes I guess it's not > likely for small clusters. Though one never knows ;-) > > Thanks, > > Dejan > >> Anyway, I think that explains the disconnect. Getting back to the real >> question of what needs a node list, quorum is the only thing I can think of. >> >> _______________________________________________ >> discuss mailing list >> discuss@xxxxxxxxxxxx >> http://lists.corosync.org/mailman/listinfo/discuss > _______________________________________________ > discuss mailing list > discuss@xxxxxxxxxxxx > http://lists.corosync.org/mailman/listinfo/discuss _______________________________________________ discuss mailing list discuss@xxxxxxxxxxxx http://lists.corosync.org/mailman/listinfo/discuss
