duplicate hdc partition table

Hi List

I managed to boot into my Raid, now I would like to add the 'failed-disk':

 raidhotadd /dev/md/1 /dev/hda3

gives me:
/dev/md/1: can not hot-add disk: too small disk!


sfdisk --force /dev/hdc | sfdisk /dev/hda

gives me:

Checking that no-one is using this disk right now ...
Checking that no-one is using this disk right now ...
BLKRRPART: Device or resource busy
 
This disk is currently in use - repartitioning is probably a bad idea.
Umount all file systems, and swapoff all swap partitions on this disk.
Use the --no-reread flag to suppress this check.
Use the --force flag to overrule all checks.
BLKRRPART: Device or resource busy

Any idea how I could raidhotadd /dev/hda or to duplicate my hdc partition table to hda?

Thanks for your time and help.

Zeno