Hi Yiping, To add to Paul's comment, you also need to understand the goal of the anti-affinity groups. If they don't care, you should simply block the command so that your users don't use it (you should list the createAffinityGroup command as a root admin call in the commands.properties file by changing it's flag value). The goal is to spread a group of VMs, a cluster of a service, so that in case of a hardware failure on one hyperisor, the cluster can be sure that only 1 of its instances will go down and the srvice can keep running.
On Thu, Jan 11, 2018 at 9:01 AM, Paul Angus <paul.an...@shapeblue.com> wrote: > Hi Yiping, > > Anti-affinity groups deal with the placement of VMs when they are started, > but doesn't/can't 'move' running VMs (it isn't like vSphere DRS). If you > change a VM's anti-affinity group, it's current placement on a host may > suddenly become invalid. As the Anti-Affinity group code isn't designed to > move VMs, the safest option is to ensure that the VM is stopped when its > group is changed so that when it is started again, CloudStack can then > properly decide where it can/should go. > > > > Kind regards, > > Paul Angus > > paul.an...@shapeblue.com > www.shapeblue.com > 53 Chandos Place, Covent Garden, London WC2N 4HSUK > @shapeblue > > > > > -----Original Message----- > From: Yiping Zhang [mailto:yzh...@marketo.com] > Sent: 10 January 2018 19:51 > To: users@cloudstack.apache.org > Subject: why instance must be stopped in order to update its affinity > groups? > > Hi, List: > > Can someone please explain why a VM instance must be in stopped state when > updating its affinity group memberships? This requirement is in “Feature > assumptions” section of the original 4.2 design document ( > https://cwiki.apache.org/confluence/display/CLOUDSTACK/ > FS+-+Affinity-Anti-affinity+groups). > > My users either don’t understand or don’t care about affinity groups and I > see a large number of instances with sub-optimal host placement (from > anti-host affinity group point of view). But it is too much trouble for me > to coordinate with so many users to shut them down in order to fix their > host placement. What bad things would happen if a running instance’s > affinity group is changed? > > Thanks, > > Yiping > >
