Hi Digimer, Thanks for your reply. On 22/06/16 15:20, Digimer wrote: > On 22/06/16 01:01 AM, Tom Robinson wrote: >> Hi, >> >> I have two KVM hosts (CentOS 7) and would like them to operate as High Availability servers, >> automatically migrating guests when one of the hosts goes down. >> >> My question is: Is this even possible? All the documentation for HA that I've found appears to not >> do this. Am I missing something? > > Very possible. It's all I've done for years now. > > https://alteeve.ca/w/AN!Cluster_Tutorial_2 > > That's for EL 6, but the basic concepts port perfectly. In EL7, just > change out cman + rgmanager for pacemaker. The commands change, but the > concepts don't. Also, we use DRBD but you can conceptually swap that for > "SAN" and the logic is the same (though I would argue that a SAN is less > reliable). In what way is the SAN method less reliable? Am I going to get into a world of trouble going that way? > > There is an active mailing list for HA clustering, too: > > http://clusterlabs.org/mailman/listinfo/users I've had a brief look at the web-site. Lots of good info there. Thanks! > >> My configuration so fare includes: >> >> * SAN Storage Volumes for raw device mappings for guest vms (single volume per guest). >> * multipathing of iSCSI and Infiniband paths to raw devices >> * live migration of guests works >> * a cluster configuration (pcs, corosync, pacemaker) >> >> Currently when I migrate a guest, I can all too easily start it up on both hosts! There must be some >> way to fence these off but I'm just not sure how to do this. > > Fencing, exactly. > > What we do is create a small /shared/definitions (on gfs2) to host the > VM XML definitions and then undefine the VMs from the nodes. This makes > the servers disappear on non-cluster aware tools, like > virsh/virt-manager. Pacemaker can still start the servers just fine and > pacemaker, with fencing, makes sure that the server is only ever running > on one node at a time. That sounds simple enough :-P. Although, I wanted to be able to easily open VM Consoles which I do currently through virt-manager. I also use virsh for all kinds of ad-hoc management. Is there an easy way to still have my cake and eat it? We also have a number of Windows VM's. Remote desktop is great but sometimes you just have to have a console. > We also have an active freenode IRC channel; #clusterlabs. Stop on by > and say hello. :) Will do. I have a bit of reading now to catch up but I'm sure I'll have a few more questions before long. Kind regards, Tom
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