On Fri, Feb 22, 2013 at 01:36:20PM -0800, Prachi Damle wrote: > Hey all, > > It seems that host affinity usecase has little value in reality and very less > guarantee of success given the current deployment planning mechanism. > > The feature requirement says host affinity = same host. So VM's in the host > affinity group, should get placed on the same host. But this is not required > in most of the real applications. > Also with Cloudstack's deployment mechanism, the affinity rules will not kick > in for the first VM. So it may get placed on a host which has not much > capacity left since at that point planners have no idea of the user's > intention. Thus if a user has a set of VMS and chooses host-affinity group, > it is possible that deployment of other VMS in the group start failing. > > So I am planning to not add the implementation for host affinity. Host > anti-affinity support however is important and needed. > > The feature will still include: > - framework for supporting affinity groups in general > - Default implementation for host anti-affinity > - DeploymentPlanningManager changes > > Any thoughts/comments? I will update the FS if this sounds correct.
+1 from me. I think your analysis is spot-on. Anti-affinity is valuable, but affinity is questionable due to it's implications.
