Den tors 5 mars 2020 kl 08:13 skrev Stefan Priebe - Profihost AG < s.priebe@xxxxxxxxxxxx>: > >> Hrm. We have checksums on the actual OSD data, so it ought to be > >> possible to add these to the export/import/diff bits so it can be > >> verified faster. > >> (Well, barring bugs.) > >> > > I mainly meant bugs, I should have clarified that better. > > > > Do you trust the technology you want to backup to create the proper > > backup for you? With that I mean, what if librbd or librados contains a > > bug which corrupts all your backups? > > > > You think the backups all went fine because the snapshots seem > > consistent on both ends, but you are not sure until you actually test a > > restore. > > Yes and know. If the object checksums inside ceph are equal it must be a > really bad bug. Sure this can happen but i think the chances are very low > Are we talking about checksums from months ago when it was created or the "current" data, which may or may not have been changed or not fully copied over to the destination in this case? It smells a bit like shuffling around the vocabulary in order to try not to end up in "dang, in order to actually know, some part must actually read 100TB data" which I think is where you have to go in order for you to move from "I think its ok" to "I know it is ok" after a copy/move/rebuild from A to B. I'm not trying to be obtuse or anything, just noting that when you sync something from A to B and ceph claims it is there, it has done as good as it can to check that the operation was done 100%. There might be reasons for distrusting this or not, but when you DO decide to mistrust, it feels weird to move backwards again and go "well, tcp checksums would have caught transmission errors, filesystem/OSD checksums should have caught storage errors and ..." because the idea if I understood it correctly to begin with was how to remove doubt about that all the various levels of operations have actually managed to create a perfect copy or not, not just list things that helped ceph make it probably-ok-but-I-dont-know to begin with. -- 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
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