If you are so worried about the storage efficiency: why not use erasure coding? EC performs really well with Luminous in our experience. Yes, you generate more IOPS and somewhat more CPU load and a higher latency. But it's often worth a try.
Simple example for everyone considering 2/1 replicas: consider 2/2 erasure coding. * Data durability and availability of 3/2 replicas * Storage efficiency of 2/1 replicas * 33% more write IOPS than 3/2 replicas * 100% more read IOPS than any replica setup (400% more to reduce latency with fast_read) Of course, 2/2 erasure coding might seem stupid. We typically use 4/2, 5/2, or 5/3. So If you are worried about reducing storage overhead: try it out and see for yourself how it performs for your use case. I've rescued several clusters that were configured with 2/1 replica and broke down in various ways... it's not pretty and can be annoying and time-consuming to fix. As in tracking down a broken disk where the OSD doesn't start up properly and trying get the last copy of a PG off it with ceph-objectstore-tool... Paul 2018-05-25 9:48 GMT+02:00 Janne Johansson <[email protected]>: > > > Den fre 25 maj 2018 kl 00:20 skrev Jack <[email protected]>: > >> On 05/24/2018 11:40 PM, Stefan Kooman wrote: >> >> What are your thoughts, would you run 2x replication factor in >> >> Production and in what scenarios? >> Me neither, mostly because I have yet to read a technical point of view, >> from someone who read and understand the code >> >> I do not buy Janne's "trust me, I am an engineer", whom btw confirmed >> that the "replica 3" stuff is subject to probability and function to the >> cluster size, thus is not a generic "always-true" rule >> > > I did not call for trust on _my_ experience or value, but on the ones > posting the > first "everyone should probably use 3 replicas" over which you showed > doubt. > I agree with them, but did not intend to claim that my post had extra > value because > it was written by me. > > Also, the last part of my post was very much intended to add "not > everything in 3x is true for everyone", > but if you value your data, it would be very prudent to listen to > experienced people who took risks and lost data before. > > > > _______________________________________________ > ceph-users mailing list > [email protected] > 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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