ZFS Panic after freebsd-update

[Scott Sipe]

On Mon, Jul 1, 2013 at 1:04 PM, Jeremy Chadwick <jdc at koitsu.org> wrote:

> On Mon, Jul 01, 2013 at 12:23:45PM -0400, Paul Mather wrote:
> > On Jul 1, 2013, at 11:49 AM, Jeremy Chadwick <jdc at koitsu.org> wrote:
> >
> > > Of course when I see lines like this:
> > >
> > >  Trying to mount root from zfs:zroot
> > >
> > >  ...this greatly diminishes any chances of "live debugging" on the
> > >  system.  It amazes me how often I see this come up on the lists --
> people
> > >  who have ZFS problems but use ZFS for their root/var/tmp/usr.  I wish
> > >  that behaviour would stop, as it makes debugging ZFS a serious PITA.
> > >  This comes up on the list almost constantly, sad panda.
> >
> >
> > I'm not sure why it amazes you that people are making widespread use of
> ZFS.
>
> It's not widespread use of ZFS.  It's widespread use of ZFS as their
> sole filesystem (specifically root/var/tmp/usr, or more specifically
> just root/usr).  People are operating with the belief that "ZFS just
> works", when reality shows "it works until it doesn't".  The mentality
> seems to be "it's so rock solid it'll never break" along with "it can't
> happen to me".  I tend to err on the side of caution, hence avoidance of
> ZFS for critical things like the aforementioned.
>
> It's different if you have a UFS root/var/tmp/usr and ZFS for everything
> else.  You then have a system you can boot/use without issue even if ZFS
> is crapping the bed.
>


> ...
>


> 95% of FreeBSD users cannot debug kernel problems**.  To debug a kernel
> problem, you need: a crash dump, a usable system with the exact
> kernel/world where the crash happened (i.e. you cannot crash 8.4 ZFS and
> boot into 8.2 and reliably debug it using that), and (most important of
> all) a developer who is familiar with kernel debugging *and* familiar
> with the bits which are crashing.  Those who say what you're quoting are
> often the latter.
>


> ...
>


> But the OP is running -RELEASE, and chooses to run that, along with use
> of freebsd-update for binary updates.  Their choices are limited: stick
> with 8.2, switch to stable/X, cease use of ZFS, or change OSes entirely.
>

So I realize that neither 8.2-RELEASE or 8.4-RELEASE are stable, but I
ultimately wasn't sure where the right place to go for discuss 8.4 is?
Beyond the FS mailing list, was there a better place for my question? I'll
provide the other requested information (zfs outputs, etc) to wherever
would be best.

This is a production machine (has been since late 2010) and after tweaking
some ZFS settings initially has been totally stable. I wasn't incredibly
closely involved in the initial configuration, but I've done at least one
binary freebsd-update previously.

Before this computer I had always done source upgrades. ZFS (and the
thought of a panic like the one I saw this weekend!) made me leery of doing
that. We're a small business--we have this server, an offsite backup
server, and a firewall box. I understand that issues like this are are
going to happen when I don't have a dedicated testing box, I just like to
try to minimize them and keep them to weekends!

It sounds like my best bet might be to add a new UFS disk, do a clean
install of 9.1 onto that disk, and then import my existing ZFS pool?

Thanks,
Scott