On Tue, Sep 15, 2015 at 8:04 AM, Eduard Matei < eduard.ma...@cloudfounders.com> wrote:
> Hi, > > This all started when we were testing Evacuate with our storage driver. > We thought we found a bug (https://bugs.launchpad.net/cinder/+bug/1491276) > then Scott replied that we should be running cinder-volume service separate > from nova-compute. > For some internal reasons we can't do that - yet, but we have some > questions regarding the behavior of the service: > > - on our original test setup we have 3 nodes (1 controller + compute + > cinder, 2 compute + cinder). > -- when we shutdown the second node and tried to evacuate, the call was > routed to cinder-volume of the halted node instead of going to other nodes > (there were still 2 cinder-volume services up) - WHY? > - on the new planned setup we will have 6 nodes (3 dedicated controller + > cinder-volume, 3 compute) > -- in this case which cinder-volume will manage which volume on which > compute node? > -- what if: one compute node and one controller go down - will the > Evacuate still work if one of the cinder-volume services is down? How can > we tell - for sure - that this setup will work in case ANY 1 controller and > 1 compute nodes go down? > > Hypothetical: > - if 3 dedicated controller + cinder-volume nodes work can perform > evacuate when one of them is down (at the same time with one compute), WHY > can't the same 3 nodes perform evacuate when compute services is running on > the same nodes (so 1 cinder is down and 1 compute) > - if the answer to above question is "They can't " then what is the > purpose of running 3 cinder-volume services if they can't handle one > failure? > - and if the answer to above question is "You only run one cinder-volume" > then how can it handle failure of controller node? > > Thanks, > > Eduard > > __________________________________________________________________________ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > Not sure I follow all your permutations and things here. But... one common misconception about multiple c-vol services; The act of just "deploying multiple c-vols" doesn't mean you get any sort of HA or failover. The default/base case for multiple c-vols is actually just for scale out and that's it. If you want to actually do things like have them fail over you have to look at configuring the c-vol services with virtual-ips and using the same name for each service etc. In other words, do a true HA deployment. Maybe I'm not following here but it sounds like maybe you have the wrong expectations around what multiple c-vol services buys you.
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