degraded zfs slowdown

[Randy Bush]

i managed to tell the controller to ignore the bad drive.  now i have

    # zpool status
      pool: tank
     state: DEGRADED
    status: One or more devices could not be used because the label is missing or
	    invalid.  Sufficient replicas exist for the pool to continue
	    functioning in a degraded state.
    action: Replace the device using 'zpool replace'.
       see: http://www.sun.com/msg/ZFS-8000-4J
     scrub: none requested
    config:

	    NAME        STATE     READ WRITE CKSUM
	    tank        DEGRADED     0     0     0
	      mirror    DEGRADED     0     0     0
		twed1   FAULTED      0     6     0  corrupted data
		twed1   ONLINE       0     0     0

    errors: No known data errors

with zfs whining

    Mar 14 15:05:20 psg root: ZFS: vdev failure, zpool=tank type=vdev.corrupt_data
    Mar 14 15:05:50 psg root: ZFS: vdev failure, zpool=tank type=vdev.corrupt_data
    Mar 14 15:07:50 psg last message repeated 4 times

as the ghostly bad drive does not have a unique name, [how] can i tell
zfs to remove it for the moment?

randy