Unplugging disk under ZFS yield panic

[Gergely CZUCZY]

Dear List,

I'd like to ask, whether it is normal behaviour when we're unplugging a
disk under a ZFS system then on the first write a kernel panic happened.

The hardware is a supermicro X8DTH-i/6/iF/6F board with 2x LSI 2008
fusion MPT SAS-2 controllers, over the mps(4) driver. The disks are
accessed over gmultipath, and the multipath'd devices are added to a
ZFS mirror:
DB
 mirror-0
  multipath/DB01
  multipath/DB02
 mirror-1
  multipath/DB03
  multipath/DB04
 logs
  mirror/host1p5
 cache
  multipath/SSD03p1
 spares
  multipath/DB05

System is 9.0-RELEASE

I've unplugged DB03 and on the first write we got a kernel panic.
Should this be normal behaviour or we're missing something here?

On a device removal we're expecting it to moving to the spare disk, or
using the available redundant disks.

Best regards,
Gergely