Cannot import raidz pool after zero fill one hdd.

[Bartosz Stec]

Hello list.

I'm not sure if it was my terrible mistake or some bug, but at this 
moment my filesystem is unbootable and unimportable from fixit 
environment and I'm pulling my hair off :(.
Here's how it happened:

I have a raidz pool consists of 3 HDD - ad0, ad1, ad2. It's zfs-only 
i386-CURRENT system created by guide 
http://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/RAIDZ1.
Smartctl has showing some warnings about offline uncorrectable sectors 
on ad0 every reboot, so I've decided to get rid of this by filling hdd 
with zeroes, rebuilding gpt table and resilver zfs partition. So what I 
did was:

zpool offline zroot gpt/disk0
swapoff gpt/swap0
sysctl kern./geom/.debugflags=/0x10/
dd if=/dev/zero of=/dev/ad0 bs=1M

After a while I've checked zpool status and ad0 was indeed offline, but 
with about 200  errors? Shouldn't  ZFS stop using this drive at all?
A moment later I tried to run bash script but I got i/o error. zpool 
status showed some unrecoverable error in this file and in some 
libraries. My guess was that zpool was still trying to use partition 
gpt/disk0 which is offline, so to avoid fs corruption I've shutdown my 
system and booted parted magic bootCD which has zerofill utility, and 
ad0 was filled with zeroes.

After reboot loader shows some LBA errors and that it cannot find zpool. 
I've booted this machine using about month old freebsd-current snapshot 
and got into fixit environment.
Here's output of zpool import: 
http://img715.imageshack.us/img715/7860/19843139.jpg

Zroot is in UNAVAIL state because of ad2p3 OFFLINE (which was never 
offline), gpt/disk1 UNAVAIL, which is the same partition as ad1p3 which 
is showed as ONLINE.

ad1p3 (gpt/disk1) and ad2p3 (gpt/disk2) should be both online and alive 
because I didn't do anything with them. I played with labels to correct 
this situation bu without success. I'm out of ideas, maybe some of you 
could help with this mess. Taking ad2p3 online should be enough but is 
it possible without importing pool? Google isn't really helpful with 
that case.

Just to be sure if I filled correct drive with zeroes I checked output 
of 'head /dev/ad[0-2]p3.  ad[1-2]p3 contain data so there was no mistake 
in there.
BUT I could made a mistake in other place - I didn't checked if 
gpt/disk0 lays for sure on ad0 :( Maybe this is a cause of trouble - ad2 
could be offline and zeroes flied to ad0 which was online. Hovewer, 
system should be still alive if I could revert offline state of ad2p3.

Thanks in advance for help .

-- 
Bartosz