Ceph

"ceph-disk prepare" can be fed a block device (e.g. /dev/sda), or a partition (e.g. /dev/sda1) as a device argument.
When provided a block device argument, ceph-disk partitions the device, and sets the corresponding GPT GUIDS, based on whether the partition is data, journal, dmcrypt, etc.
However, if ceph-disk is a given partition device argument it leaves the GPT GUID as is, and doesn't check that the partition's GPT GUID matches the prepared partition type. As a result, components that rely on the partition GUID (e.g. udev) may fail.

I plan on proposing a patch that dumps a loud warning if "ceph-disk prepare" is called with a partition device argument, and the partition device's GUID doesn't match the expected Ceph reserved value.