IIRC this will create a rule that tries to selects n independent data centers Check the actual generated rule to validate this.
I think the only way to express "3 copies across two data centers" is by explicitly using the two data centers in the rule as in: (pseudo code) take dc1 chooseleaf 1 type host emit take dc2 chooseleaf 2 type host emit Which will always place 1 on dc1 and 2 in dc2. A rule like take default choose 2 type datacenter chooseleafe 2 type host emit will select a total of 4 hosts in two different data centers (2 hosts per dc) But the real problem here is that 2 data centers in one Ceph cluster is just a poor fit for Ceph in most scenarios. 3 would be fine. Two independent clusters and async rbd-mirror or rgw synchronization would also be fine. But one cluster in two data centers and replicating via CRUSH just isn't how it works. Maybe you are looking for something like "3 independent racks" and you happen to have two racks in each dc? Really depends on your setup and requirements. Paul 2018-08-13 14:09 GMT+02:00 Torsten Casselt <cass...@luis.uni-hannover.de>: > Hi, > > I created a rule with this command: > > ceph osd crush rule create-replicated rrd default datacenter > > Since chooseleaf type is 1, I expected it to distribute the copies > evenly on two datacenters with six hosts each. For example, six copies > would mean a copy on each host. > > When I test the resulting CRUSH map with the crush tool I get bad > mappings. PGs stay in active+clean+remapped and > active+undersized+remapped. I thought it might help if I increase the > choose tries, but it stays the same. > > What is the best method to distribute at least three copies over two > datacenters? Since the docs state that it is rarely needed to decompile > the CRUSH map, I thought it must be possible with a rule create command > like above. I don’t think it is that rare to have two sites… > > Thanks! > Torsten > > -- > Torsten Casselt, IT-Sicherheit, Leibniz Universität IT Services > Tel: +49-(0)511-762-799095 Schlosswender Str. 5 > Fax: +49-(0)511-762-3003 D-30159 Hannover > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > -- Paul Emmerich Looking for help with your Ceph cluster? Contact us at https://croit.io croit GmbH Freseniusstr. 31h 81247 München www.croit.io Tel: +49 89 1896585 90
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