cgd gives read-only error

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

I just tried the "To scrub data from a disk before setting up a cgd"
recipe from cgdconfig on a new amd64 box installed from 12th December 
current dist files. For some reason the dd fails with /dev/rcgd0d
is a read-only file system.

The cgd0 is created from raid1a which is a partition of raid1 which
in turn is over dk2 and dk7 from two gpt partitioned disks wd2 and wd3.

I can dd zeros all over rraid1d. I can newfs and mount cgd0a, and read
and write from/to it. So why can't I write to rcgd0d?

A murky recollection is that raid1e, raid1f and raid1g scrub correctly.
raid2a also fails. Is there something special about the first partition?
(Take with pinch of salt..)

Puzzled...

Cheers,

Patrick