On 02-11-15 12:30, Loris Cuoghi wrote: > Hi All, > > We're currently on version 0.94.5 with three monitors and 75 OSDs. > > I've peeked at the decompiled CRUSH map, and I see that all ids are > commented with '# Here be dragons!', or more literally : '# do not > change unnecessarily'. > > Now, what would happen if an incautious user would happen to put his > chubby fingers on this ids, totally disregarding the warning at the > entrance of the cave, and change one of them? > > Data shuffle? (Relative to the allocation of PGs for the OSD/host/other > item?) > > A *big* data shuffle? (ALL data would need to have its position > recalculated, with immediate end-of-the-world data shuffle?) > > Nothing at all? (And the big fat warning is there only to take fun on > the uninstructed ones? Not plausible...) > Give it a try! Download the CRUSHMap and run tests on it with crushtool: $ crushtool -i mycrushmap --test --rule 0 --num-rep 3 --show-statistics Now, change the map, compile it and run again: $ crushtool -i mycrushmap.new --test --rule 0 --num-rep 3 --show-statistics Check the differences and you get the idea of how much has changed. Wido > Thanks ! > > Loris > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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