On 10/11/2018 02:58 PM, Sage Weil wrote: > > I'm worried the above it a lot of complexity and opportunity for bugs > (and work to implement) for not a lot of gain. What if we instead make > ceph-monstore-tool have a 'convert' function that will do a conversion > offline? The admin can take each mon down in turn, convert it, and bring > it back up. Provisioning tools could automate this process. > > This will require ~2x the disk space for the conversion. OTOH, if space > is tight, the user can also just blow away the mon entirely and create > it, and let the normal sync bring it back into quorum... The problem with both approaches is that, during this period, the quorum is degraded. We can argue that the way to prevent that is to add a new monitor, let it sync, and then remove an old mon, but we may not have spare hardware to make this work. I do agree that this would be a complex solution for something that would be used 3, maybe 5 times in the lifespan of a cluster< but this is also the sort of thing that shouldn't make the user jump through hoops to accomplish. -Joao
