[ceph-users] Re: removing/flattening a bucket without data movement?

Originally our osd tree looked like this: ID  CLASS WEIGHT     TYPE NAME                     STATUS REWEIGHT PRI-AFF  -1       2073.15186 root default -14        176.63100     rack s01-rack -19        176.63100         host s01 <snip osds> -15        171.29900     rack s02-rack -20        171.29900         host s02 <snip osds> etc. You get the idea. It was a legacy thing as we've been upgrading this cluster since probably firefly, and started with way less hardware. The crush rule was set up like this originally:         step take default         step chooseleaf firstn 0 type rack which we have modified to         step take default         step chooseleaf firstn 0 type host taking advantage of chooseleaf's behavior (eg searching in depth instead of just a single level). Now we thought we could get rid of the rack buckets simply by moving the host buckets to the root using "ceph osd crush move s01 root=default", however this resulted in a bunch of data movement. Swapping the IDs manually in the crushmap seems to work (verified via crushtool's --compare), eg. changing the ID of s01 to s01-rack's and vice versa, including all shadow trees. Looking around I saw that there is a swap-bucket command but that does not swap the IDs just bucket contents, so would result in data movement. Other than manually editing the crushmap is there a better way to achieve this? Is this way the most optimal?