Re: ZFS i/o error in recent 12.0

> On 20 Mar 2018, at 09:50, Markus Wild <fbsd-lists_at_dudes.ch> wrote:
> 
> Hi there,
> 
>> I've been encountered suddenly death in ZFS full volume
>> machine(r330434) about 10 days after installation[1]:
>> 
>> ZFS: i/o error - all block copies unavailable
>> ZFS: can't read MOS of pool zroot
>> gptzfsboot: failed to mount default pool zroot
>> 
> 
>>    268847104  30978715648      4  freebsd-zfs  (14T)
> 
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> 
> I had faced the exact same issue on a HP Microserver G8 with 8TB disks and a 16TB zpool on FreeBSD 11 about a year ago.
> My conclusion was, that over time (and updating the kernel), the blocks for that kernel file were reallocated to a
> later spot on the disks, and that however the loader fetches those blocks, it now failed doing so (perhaps a 2/4TB
> limit/bug with the BIOS of that server? Unfortunately, there was no UEFI support for it, don't know whether that
> changed in the meantime). The pool was always importable fine with the USB stick, the problem was only with the boot
> loader. I worked around the problem stealing space from the swap partitions on two disks to build a "zboot" pool, just
> containing the /boot directory, having the boot loader load the kernel from there, and then still mount the real root
> pool to run the system off using loader-variables in loader.conf of the boot pool. It's a hack, but it's working
> fine since (the server is being used as a backup repository). This is what I have in the "zboot" boot/loader.conf:
> 
> # zfs boot kludge due to buggy bios
> vfs.root.mountfrom="zfs:zroot/ROOT/fbsd11"
> 
> 
> If you're facing the same problem, you might give this a shot? You seem to have plenty of swap to canibalize as well;)
> 

please check with lsdev -v from loader OK prompt - do the reported disk/partition sizes make sense. Another thing is, even if you do update the current build, you want to make sure your installed boot blocks are updated as well - otherwise you will have new binary in the /boot directory, but it is not installed on boot block area…

rgds,
toomas