On Wed, Sep 13, 2017 at 11:04 AM, Dan van der Ster <d...@vanderster.com> wrote: > On Wed, Sep 13, 2017 at 10:54 AM, Wido den Hollander <w...@42on.com> wrote: >> >>> Op 13 september 2017 om 10:38 schreef Dan van der Ster >>> <d...@vanderster.com>: >>> >>> >>> Hi Blair, >>> >>> You can add/remove mons on the fly -- connected clients will learn >>> about all of the mons as the monmap changes and there won't be any >>> downtime as long as the quorum is maintained. >>> >>> There is one catch when it comes to OpenStack, however. >>> Unfortunately, OpenStack persists the mon IP addresses at volume >>> creation time. So next time you hard reboot a VM, it will try >>> connecting to the old set of mons. >>> Whatever you have in ceph.conf on the hypervisors is irrelevant (after >>> a volume was created) -- libvirt uses the IPs in each instance's xml >>> directly. >>> >> >> That's why I always recommend people to use DNS and preferably a Round Robin >> DNS record to overcome these situations. >> >> That should work with OpenStack as well. >> >> ceph-mon.storage.local. AAAA 2001:db8::101 >> ceph-mon.storage.local. AAAA 2001:db8::102 >> ceph-mon.storage.local. AAAA 2001:db8::103 >> >> And then use *ceph-mon.storage.local* in your OpenStack configuration a MON. >> > > Does that work? Last time I checked, it works like this when a new > volume is attached: > > - OpenStack connects to ceph using ceph.conf, DNS, whatever... > - Retrieve the monmap. > - Extract the list of IPs from the monmap. > - Persist the IPs in the block-device-mapping table. > > I still find that logic here: > https://github.com/openstack/nova/blob/master/nova/virt/libvirt/storage/rbd_utils.py#L163 >
And here's that same approach in the Cinder driver: https://github.com/openstack/cinder/blob/master/cinder/volume/drivers/rbd.py#L350 -- dan > Next time you hard-reboot the VM, it will connect to the IPs directly > -- not use ceph.conf or DNS. > > -- Dan > > > >> Wido >> >>> There is an old ticket here: https://bugs.launchpad.net/cinder/+bug/1452641 >>> It's recently gone unassigned, but there is a new proposed fix here: >>> http://lists.openstack.org/pipermail/openstack-dev/2017-June/118040.html >>> >>> As of today, you will need to manually update nova's >>> block-device-mapping table for every volume when you re-ip the mons. >>> >>> Cheers, Dan >>> >>> >>> On Wed, Sep 13, 2017 at 4:57 AM, Blair Bethwaite >>> <blair.bethwa...@gmail.com> wrote: >>> > Hi all, >>> > >>> > We're looking at readdressing the mons (moving to a different subnet) >>> > on one of our clusters. Most of the existing clients are OpenStack >>> > guests on Libvirt+KVM and we have a major upgrade to do for those in >>> > coming weeks that will mean they have to go down briefly, that will >>> > give us an opportunity to update their libvirt config to point them at >>> > new mon addresses. We plan to do the upgrade in a rolling fashion and >>> > thus need to keep Ceph services up the whole time. >>> > >>> > So question is, can we for example have our existing 3 mons on network >>> > N1, add another 2 mons on network N2, reconfigure VMs to use the 2 new >>> > mon addresses, all whilst not impacting running clients. You can >>> > assume we'll setup routing such that the new mons can talk to the old >>> > mons, OSDs, and vice-versa. >>> > >>> > Perhaps flipping the question on its head - if you configure a librbd >>> > client with only a subset of mon addresses will it *only* talk to >>> > those mons, or will it just use that config to bootstrap and then talk >>> > to any mons that are up in the current map? Or likewise, is there >>> > anything the client has to talk to the mon master for? >>> > >>> > -- >>> > Cheers, >>> > ~Blairo >>> > _______________________________________________ >>> > ceph-users mailing list >>> > ceph-users@lists.ceph.com >>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>> _______________________________________________ >>> ceph-users mailing list >>> ceph-users@lists.ceph.com >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
