GPT boot with ZFS RAIDZ "ZFS: i/o error - all block copies unavailable"

[Emil Smolenski]

  After installkernel/installworld my machine stops booting with the  
following error message:

ZFS: i/o error - all block copies unavailable
ZFS: can't read MOS
ZFS: unexpected object set type lld

FreeBSD/i386 boot
Default: pgpool:/boot/kernel/kernel
boot:
ZFS: unexpected object set type lld

  This is 7.2-STABLE, amd64, zpool on single logical device (ciss(4),  
hardware RAID5), root on ZFS (using zfsboot). After the failure I booted  
the server from an external device with UFS and then I did rollback of  
/usr and / datasets. The machine was still not bootable. Scrub went  
without errors.
  Then I read this thread and applied Robert Noland's and Matt Reimer's  
patches -- and they didn't help. Then I grabbed following files from  
-CURRENT (svn rev. 198420):

/sys/boot/i386/zfsboot/zfsboot.c
/sys/boot/zfs/zfs.c
/sys/boot/zfs/zfsimpl.c
/sys/cddl/boot/zfs/zfsimpl.h

and I did:

# cd /usr/src/sys/boot/
# make obj ; make depend ; make
# cd i386/loader
# make install
# cd /usr/src/sys/boot/i386/zfsboot
# make install
# sysctl kern.geom.debugflags=16
# dd if=/boot/zfsboot of=/dev/da0 count=1
# dd if=/boot/zfsboot of=/dev/da0 skip=1 seek=1024
# reboot

  (is this procedure of updating zfsboot correct?)

  After that, an error was slightly different (printf was fixed):

ZFS: i/o error - all block copies unavailable
ZFS: can't read MOS
ZFS: unexpected object set type 0

FreeBSD/i386 boot
Default: pgpool:/boot/kernel/kernel
boot:
ZFS: unexpected object set type 0

  Additional information:

# zpool list
NAME     SIZE   USED  AVAIL    CAP  HEALTH  ALTROOT
pgpool  4.06T  2.17T  1.89T    53%  ONLINE  -

# zpool status
   pool: pgpool
  state: ONLINE
  scrub: none requested
config:

         NAME        STATE     READ WRITE CKSUM
         pgpool      ONLINE       0     0     0
           da0       ONLINE       0     0     0

errors: No known data errors

# zfs list pgpool/ROOTFS
NAME           USED  AVAIL  REFER  MOUNTPOINT
pgpool/ROOTFS  568M  1.80T  55.3M  legacy

# zpool get all pgpool
NAME    PROPERTY       VALUE          SOURCE
pgpool  size           4.06T          -
pgpool  used           2.17T          -
pgpool  available      1.89T          -
pgpool  capacity       53%            -
pgpool  altroot        -              default
pgpool  health         ONLINE         -
pgpool  guid           3920915583055727184  -
pgpool  version        13             default
pgpool  bootfs         pgpool/ROOTFS  local
pgpool  delegation     on             default
pgpool  autoreplace    off            default
pgpool  cachefile      -              default
pgpool  failmode       wait           default
pgpool  listsnapshots  off            default

  loader.conf:
usb_load="YES"
uplcom_load="YES"
umass_load="YES"
ugen_load="YES"
ukbd_load="YES"
random_load="YES"
loader_color="YES"
vfs.root.mountfrom="zfs:pgpool/ROOTFS"
zfs_load="YES"
autoboot_delay="2"

FreeBSD 7.2-STABLE #0: Fri Jun 19 13:27:29 CEST 2009
(as I mentioned above, there was the rollback)

ciss0: <HP Smart Array P400> port 0xe800-0xe8ff mem  
0xdef00000-0xdeffffff,0xdeeff000-0xdeefffff irq 35 at device 0.0 on pci4
ciss0: [ITHREAD]
da0 at ciss0 bus 0 target 0 lun 0

  I would rather not to upgrade the whole system to -CURRENT. What should I  
do in this situation? Is there any other patch that I could apply or any  
workaround for this issue? Is there possibility to switch from zfsboot to  
gptzfsboot without loosing data? Or maybe I did something wrong?

-- 
am