Many of the features supported by Ceph for image formats on a Rados Block Device are not yet supported by the kernel module included with UEK R4 update 2. This can cause problems when mapping an image to a block device resulting in the following error:

# rbd map vol1 --pool datastore
rbd: sysfs write failed
RBD image feature set mismatch. You can disable features unsupported by the
kernel with "rbd feature disable".
In some cases useful info is found in syslog - try "dmesg | tail" or so.
rbd: map failed: (6) No such device or address

This requires that when the image is created the appropriate features are enabled manually or that you change the default feature set in the Ceph configuration.

Workaround: To resolve this issue, edit /etc/ceph/ceph.conf to include the line:

rbd default features = 3

Alternatively enable the layering feature when creating the image, by using the --image-feature switch. For example:

# rbd create vol1 --size 250 --pool datastore --image-feature layering

(Bug 23562267)