osd_fsid does not exist, fsid is generated instead
Not sure if this is a bug or incorrect documentation. Documentation (http://docs.ceph.com/docs/master/ceph-volume/lvm/activate/) states: "Note
The UUID is stored in the osd_fsid file in the OSD path, which is generated when prepare is used."
However there is no osd_fsid there, only a "fsid" (not the cluster fsid). This makes it pretty confusing. So either the documentation is wrong and should be fixed, or the code should be fixed and put the OSD FSID/UUID in the file osd_fsid. I prefer the latter, just to avoid confusion.