gmirror: Not all disks connected

I've installed 5.4-rc3 recently and decided to play with geom gmirror. I
have two fresh SAMSUNG SP0411N/TW100-11, so I've put it together and
followed steps described in http://people.freebsd.org/~rse/mirror/.
Everything was ok, but when I rebooted with "the final two-disk GEOM
mirror setup", I've noticed what it's probably still one disk in gm0:

Timecounter "TSC" frequency 1817908512 Hz quality 800
Timecounters tick every 10.000 msec
ad0: 38203MB <SAMSUNG SP0411N/TW100-11> [77619/16/63] at ata0-master
UDMA100
ad1: 38204MB <SAMSUNG SP0411N/TW100-11> [77622/16/63] at ata0-slave
UDMA100
GEOM_MIRROR: Device gm0 created (id=2404813840).
GEOM_MIRROR: Device gm0: provider ad1 detected.
GEOM_MIRROR: Force device gm0 start due to timeout.
GEOM_MIRROR: Device gm0: provider ad1 activated.
GEOM_MIRROR: Device gm0: provider mirror/gm0 launched.
Mounting root from ufs:/dev/mirror/gm0s1a


Well, maybe I've lost last changes ang gmirror still lives with ad1 only? 

cymbal# gmirror list
Geom name: gm0
State: DEGRADED
Components: 2
Balance: round-robin
Slice: 4096
Flags: NONE
GenID: 0
SyncID: 3
ID: 2404813840
Providers:
1. Name: mirror/gm0
	   Mediasize: 40060403200 (37G)
	   Sectorsize: 512
	   Mode: r7w7e2
Consumers:
1. Name: ad1
   Mediasize: 40060403712 (37G)
   Sectorsize: 512
   Mode: r1w1e1
   State: ACTIVE
   Priority: 0
   Flags: DIRTY
   GenID: 0
   SyncID: 3
   ID: 3247857729


When I tried to repeat last steps, I got message "Not all disks connected".

cymbal# gmirror configure -a gm0
Not all disks connected.
cymbal# gmirror status
      Name    Status  Components
	  mirror/gm0  DEGRADED  ad1


It seems like gmirror think I've lost ad0, but it's ok.
I've tried to play with gmirror utility but in most cases I've got "Not
all disk connected" message.

Any help will be very appreciated. Thanks in advance.