Question about booting from detached mirror disk failed

Question

please see bellow for detail info,would you like to give me some advise on how to do this?
root@hn-t5220-test # zpool status
pool: rpool
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
rpool ONLINE 0 0 0
mirror ONLINE 0 0 0
c1t0d0s0 ONLINE 0 0 0
c1t1d0s0 ONLINE 0 0 0
errors: No known data errors
root@hn-t5220-test # zpool offline rpool c1t1d0s0
root@hn-t5220-test # zpool status
pool: rpool
state: DEGRADED
status: One or more devices has been taken offline by the administrator.
Sufficient replicas exist for the pool to continue functioning in a
degraded state.
action: Online the device using 'zpool online' or replace the device with
'zpool replace'.
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
rpool DEGRADED 0 0 0
mirror DEGRADED 0 0 0
c1t0d0s0 ONLINE 0 0 0
c1t1d0s0 OFFLINE 0 0 0
errors: No known data errors
root@hn-t5220-test # zpool detach rpool c1t1d0s0
root@hn-t5220-test #
root@hn-t5220-test #
root@hn-t5220-test # init 0
root@hn-t5220-test # svc.startd: The system is coming down. Please wait.
svc.startd: 96 system services are now being stopped.
Mar 23 21:13:39 hn-t5220-test syslogd: going down on signal 15
svc.startd: The system is down.
syncing file systems... done
Program terminated
ChassisSerialNumber BEL0848KRT
SPARC Enterprise T5220, No Keyboard
Copyright 2008 Sun Microsystems, Inc. All rights reserved.
OpenBoot 4.29.0.a, 65408 MB memory available, Serial #85045372.
Ethernet address 0:21:28:11:b0:7c, Host ID: 8511b07c.
{0} ok boot mirrdisk
Boot device: /pci@0/pci@0/pci@2/scsi@0/disk@1,0:a File and args:
SunOS Release 5.10 Version Generic_137137-09 64-bit
Copyright 1983-2008 Sun Microsystems, Inc. All rights reserved.
Use is subject to license terms.
NOTICE:
* This device is not bootable! *
* It is either offlined or detached or faulted. *
* Please try to boot from a different device. *
NOTICE:
spa_import_rootpool: error 22
Cannot mount root on /pci@0/pci@0/pci@2/scsi@0/disk@1,0:a fstype zfs
panic[cpu0]/thread=180e000: vfs_mountroot: cannot mount root
000000000180b950 genunix:vfs_mountroot+358 (800, 200, 0, 18a7c00, 18d1400, 18fa400)
%l0-3: 00000000010d1000 00000000010d0fa0 00000000018ad7b8 00000000011fd800
%l4-7: 00000000011fd800 00000000018fc800 0000000000000600 0000000000000200
000000000180ba10 genunix:main+a0 (182b548, 180c000, 185b240, 18f6c00, 1831948, 182b400)
%l0-3: 000000000101a800 0000000000000001 0000000070002000 0000000000000000
%l4-7: 0000000001862800 0000000000000000 000000000180c000 0000000000000000
skipping system dump - no dump device configured
rebooting...

Answer 1

Why would you need to swap the drives? Couldn't you just boot from the mirror directly? If the primary disk isn't available, it should just mark that side down.
This is very different from removing a disk from the pool and then trying to use it.
Darren