Ceph

$ ceph osd getmap -o osdmap
got osdmap epoch 59
$ osdmaptool --test-map-object dmick.rbd osdmap
osdmaptool: osdmap file 'osdmap'
object 'dmick.rbd' -> 0.69c8 -> [3,1]

shows dmick.rbd mapping to pg 0.69c8, which in turn maps to OSDs 3 and 1, 3
being the primary.

You can do this more simply with:

ceph osd map <poolname> <objectname>

sage

I'd have been happy to know about ceph osd map :) But it's not in the manpage,
usage, or ceph.com/docs that I can find.