This was recently covered on the mailing list. I believe this will cover all of your questions.
https://www.spinics.net/lists/ceph-users/msg37252.html On Tue, Jul 18, 2017, 9:07 AM Laszlo Budai <[email protected]> wrote: > Dear all, > > we are planning to add new hosts to our existing hammer clusters, and I'm > looking for best practices recommendations. > > currently we have 2 clusters with 72 OSDs and 6 nodes each. We want to add > 3 more nodes (36 OSDs) to each cluster, and we have some questions about > what would be the best way to do it. Currently the two clusters have > different CRUSH maps. > > Cluster 1 > The CRUSH map only has OSDs, hosts and the root bucket. Failure domain is > host. > Our final desired state would be: > OSD - hosts - chassis - root where each chassis has 3 hosts, each host has > 12 OSDs, and the failure domain would be chassis. > > What would be the recommended way to achieve this without downtime for > client operations? > I have read about the possibility to throttle down the recovery/backfill > using > osd max backfills = 1 > osd recovery max active = 1 > osd recovery max single start = 1 > osd recovery op priority = 1 > osd recovery threads = 1 > osd backfill scan max = 16 > osd backfill scan min = 4 > > but we wonder about the situation when, in a worst case scenario, all the > replicas belonging to one pg have to be migrated to new locations according > to the new CRUSH map. How will ceph behave in such situation? > > > Cluster 2 > the crush map already contains chassis. Currently we have 3 chassis (c1, > c2, c3) and 6 hosts: > - x1, x2 in chassis c1 > - y1, y2 in chassis c2 > - x3, y3 in chassis c3 > > We are adding hosts z1, z2, z3 and our desired CRUSH map would look like > this: > - x1, x2, x3 in c1 > - y1, y2, y3 in c2 > - z1, z2, z3 in c3 > > Again, what would be the recommended way to achieve this while the clients > are still accessing the data? > > Is it safe to add more OSDs at a time? or we should add them one by one? > > Thank you in advance for any suggestions, recommendations. > > Kind regards, > Laszlo > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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