Thanks Anthony and Wesley for your input. Let me explain in more detail why I'm interested in the somewhat obscure looking procedure in step 1. Whats the difference between "ceph osd reweight" and "ceph osd crush reweight"? the difference is that command 1 only remaps shards within the same failure domain (as Anthony noted), while command 2 implies global changes to the crush map with rediúndant data movement. In other words, using ceph osd reweight osd.X 0 will only move the shards from osd.X to other OSDs (in the same failue domain) while ceph osd crush reweight osd.X 0 has a global effect and will move a lot more around. This "a lot more" is what I want to avoid. There is necessary data movement, namely the data on the OSDs I want to evacuate, and there is redundant data movement, which is everything else. So, for evacuation, the first command is the command of choice if one wants to move exactly the shards that need to move. If one re-creates OSDs with exactly the same IDs and weights that the evacuated OSDs had, which is the default when using "ceph osd destroy" as it preserves the crush weights, then, after adding the new OSDs, it will be exactly the shards that were evacuated in step 1 that will move back. That's the minimum possible data movement: data moved = data that needs to move. I don't have balancer or anything enabled that could interfere with that procedure. Please don't bother commenting about things like that. My actual question is, how dangerous is it to use ceph osd reweight osd.X 0 instead of ceph osd reweight osd.X 0.001 The first command will mark the OSD OUT while the second won't. The second command might leave 1-2 PGs on the OSDs, while the first one won't. Does the OSD being formally UP+OUT make any difference compared with UP+IN for evacuation? My initial simplistic test says no, but I would like to be a bit more sure than that. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
 |