There is currently no support for native sata hotplug in OpenBSD,
so this is expected.

On Sat, Aug 28, 2010 at 07:31:26PM +0200, Gerald Holl wrote:
quoted text
> Hello,
> 
> I'm using OpenBSD 4.7 on an IBX 530 Intel Atom[1]. If I connect an
> external SATA HDD it is not discovered and I have to reboot in order to
> mount it. If I connect the same HDD by USB hotplug works as expected. Is
> there a way to enable hotplug for eSATA devices on OpenBSD? Or is it
> restricted by the hardware?
> 
> cheers,
> Gerald
> 
> [1]
> http://www.icpamerica.com/products/single_board_computers/embedded_systems/ibx_530_945...