OSD class path issues

2011-12-05 17:41:00.994075 7ffe8b5c3760 librbd: failed to assign a block name for image
create error: error 5: Input/output error

This usually happens because your OSDs can’t find cls_rbd.so. They search for it in osd_class_dir, which may not be set correctly by default (http://tracker.ceph.com/issues/1722).

Most likely it’s looking in /usr/lib/rados-classes instead of /usr/lib64/rados-classes - change osd_class_dir in your ceph.conf and restart the OSDs to fix it.