[CentOS] zfs

Hi, folks,

   testing zfs. I'd created a zpoolz2, ran a large backup onto it. Then I
pulled one drive (11-drive, one hot spare pool), and it resilvered with
the hot spare.  zpool status -x shows me
 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://zfsonlinux.org/msg/ZFS-8000-4J
  scan: resilvered 1.91T in 29h33m with 0 errors on Tue Jun 11 15:45:59 2019
config:

	NAME         STATE     READ WRITE CKSUM
	export1      DEGRADED     0     0     0
	  raidz2-0   DEGRADED     0     0     0
	    sda      ONLINE       0     0     0
	    spare-1  DEGRADED     0     0     0
	      sdb    UNAVAIL      0     0     0
	      sdl    ONLINE       0     0     0
	    sdc      ONLINE       0     0     0
	    sdd      ONLINE       0     0     0
	    sde      ONLINE       0     0     0
	    sdf      ONLINE       0     0     0
	    sdg      ONLINE       0     0     0
	    sdh      ONLINE       0     0     0
	    sdi      ONLINE       0     0     0
	    sdj      ONLINE       0     0     0
	    sdk      ONLINE       0     0     0
	spares
	  sdl        INUSE     currently in use

but when I try zpool replace export1 /dev/sdb1, it says, nope,
invalid vdev specification
use '-f' to override the following errors:
/dev/sdb1 is part of active pool 'export1'

Any idea what I'm doing wrong?

     mark