newfs returns cg 0: bad magic number

[Willem Jan Withagen]

Hi,

I'm able to create a Ceph RBD backed ggate disk, in /dev/ggate0.
It looks like I can:
	run dd on it
	gpart the disk
	create a zpool on it

But when I try to create a UFS file system on it, newfs complains
straight from the bat.

# sudo newfs -E /dev/ggate0p1
/dev/ggate0p1: 1022.0MB (2093056 sectors) block size 32768, fragment
size 4096
        using 4 cylinder groups of 255.53MB, 8177 blks, 32768 inodes.
Erasing sectors [128...2093055]
super-block backups (for fsck_ffs -b #) at:
 192, 523520, 1046848, 1570176
cg 0: bad magic number

Googling returns that this is on and off a problem with new devices, but
there is no generic suggestion on how to debug this....

Any/all suggestions are welcome,

--WjW