slowdown of zfs (tx->tx)

[Nicolas Rachinsky]

* Artem Belevich <art at freebsd.org> [2013-01-18 08:20 -0800]:
> On Fri, Jan 18, 2013 at 3:26 AM, Nicolas Rachinsky
> <fbsd-mas-0 at ml.turing-complete.org> wrote:
> > * Artem Belevich <art at freebsd.org> [2013-01-16 00:45 -0800]:
> >> On Tue, Jan 15, 2013 at 11:37 PM, Nicolas Rachinsky
> >> <fbsd-mas-0 at ml.turing-complete.org> wrote:
> >> >> You may want to update your system to very recent FreeBSD as quite a
> >> >> few fixes were recently imported from illumos. Hopefully it will deal
> >> >> with the issue. I'm out of ideas otherwise. Sorry.
> >> >
> >> > Do you mean -CURRENT or -STABLE with very recent? Or just 9.1?
> >>
> >> -HEAD or -STABLE (-8 or -9).
> >
> > I have now updated the machine to stable/8 r245541. I have not updated
> > the zpool.
> >
> > But the problem still occurs. Should I update the pool? Or try other
> > things first?
> 
>  Updating the pool is an irreversible operation. In general I'd
> suggest trying less drastic options first.
> 
> Other people suggested that the problem may be just a side effect of
> almost-full filesystem. ZFS needs fair amount of unfragmented free
> space in order to work efficiently. If that's what's causing your
> problem, then one thing to try would be to free enough free space. The
> gotcha there is that you need to free up enough contiguous space.
> Removing bunch of recently written files may not help as those writes
> would happen on already fragmented FS. Removing files written when FS
> had a lot of free space may have better chance of freeing contiguous
> space. Old snapshots are good candidates for this.

It seems, it was too little free space.

I copied some data to another machine and deleted it from this zpool
(one part was written on the beginning of December, the other one on
the beginning of January). I removed no snapshots and no filesystems.

After this everything works fine.

Thank you all for your efforts! 

Nicolas
-- 
http://www.rachinsky.de/nicolas