Seeing the dreaded "ZFS: i/o error - all block copies unavailable" on 9.0-CURRENT

[Chris]

> I'm seeing some difference in the bootloader output between using the
> F12 workaround or not:
>
> F12 workaround mode:
>
> FreeBSD/i386 boot
> Default: zroot:/boot/zfsloader
> boot: status
> config:
>
>             NAME     STATE
>             zroot    ONLINE
>        gpt/disk0   ONLINE
>
>
> No F12 key pressed:
>
> FreeBSD/i386 boot
> Default: zroot:/boot/kernel/kernel
> config:
>
>              NAME     STATE
>               zroot    ONLINE
>          gpt/disk0   ONLINE
>
>
> What's up with the differences between the Default boot setting?
>

Sorry for the spam but I'm seeing something else very interesting....
If I boot to Good Mode (F12) and break to the "boot:" prompt, the
system boots if I type /boot/zfsloader. However, if I type
/boot/kernel/kernel (as was seen in the Default setting when I didn't
hit F12),  I get a crash that looks like the following:
-----------------------------------------
FreeBSD/i386 boot
Default: zroot:/boot/zfsloader
boot: /boot/kernel/kernel
int=00000006    err=00000000  efl=00010882  eip=00200000
eax=0018b070  ebx=ed7706bd ecx=c72e2ca8 edx=00000000
esi=00000040   edi=000929d0  ebp=0009279c esp=00009401
cs=0008  ds=0010   es=0010  fs=0010  gs=0010  ss=0010
cs:eip=ff ff ff ff ff ff ff ff 7f-00 00 00 00 00 00 00 00
           00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00
ss:esp=36 80 0d 07 90 00 00 01-e9 c4 fc ff ff aa ac 84
             c0 0f 84 86 00 00 00 a8-80 74 f2 88 c5 b0 3d aa
BTX halted
-----------------------------------------

McCoy: "He's dead, Jim."
Kirk: "Bones, do something!"