I'm facing the same issue. My cluster will have an expansion and I wanna modify the ec profile too. What I can think of is to create a new profile and a new pool, and then migrate the data from the old pool to the new one. Finally rename the pools as I can use the new pool just like nothing happened. And of course, the access will be shut down while migrating. I'm looking for a more efficient way, which has no need to stop the clients, to deal with this. Janne Johansson <icepic.dz@xxxxxxxxx> 于2020年7月29日周三 上午1:43写道： > Den tis 28 juli 2020 kl 18:50 skrev David Orman <ormandj@xxxxxxxxxxxx>: > > > Hi, > > > > As we expand our cluster (adding nodes), we'd like to take advantage of > > better EC profiles enabled by higher server/rack counts. I understand, as > > Ceph currently exists (15.2.4), there is no way to live-migrate from one > EC > > profile to another on an existing pool, for example, from 4+2 to 17+3 > when > > going from 7 nodes to 21. Is this correct? > > > > ..depends on how brave you are, but mostly it's true. > > Mostly people stick to the configured EC size(s) on the pools even if you > buy > more nodes, the EC profile doesn't have to be close to the number of nodes, > it > can well be 4+2 even with 21 nodes, it will just choose 6 random nodes out > of > the 21 for each PG and spread out evenly in your new larger cluster. > > Also, 17+3 means 20 nodes are involved in every reasonably sized IO, and > that > may not be optimal, both in terms of CPU usage, and of course that if your > previous > speed was ok when 6 nodes were needed to reassemble a piece of data, you > can now do 3 of those 4+2-IOs in parallel if your network allows. > > Also, with 17+3 on 21 nodes, then a two node failure means it is > continually degraded* > until a host comes back up, but with k+m being < 15 would mean that the > cluster can > repair itself onto those ~15 nodes and still be in full swing even if up to > 6 nodes would > be lost, however improbable such a failure would be. > > *) So the +3 normally means three hosts could fail, but having only 19 > hosts on a 17+3 > would mean it can never reach active+clean for any PG, since there > aren't 20 hosts to > use. You wouldn't lose data, but all PGs would be degraded/undersized > meaning you > run the whole cluster at 17+2 at best. > > -- > May the most significant bit of your life be positive. > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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