When will ZFS become stable?

Maciej Suszko maciej at suszko.eu
Sun Jan 6 11:56:32 PST 2008

Kris Kennaway wrote:
> Maciej Suszko wrote:
> > Kris Kennaway wrote:
> >> Maciej Suszko wrote:
> >>> Kris Kennaway wrote:
> >>>> Ivan Voras wrote:
> >>>>> On 06/01/2008, Peter Schuller <peter.schuller at infidyne.com>
> >>>>> wrote:
> >>>>>>> This number is not so large. It seems to be easily crashed by
> >>>>>>> rsync, for example (speaking from my own experience, and also
> >>>>>>> some of my colleagues).
> >>>>>> I can definitely say this is not *generally* true, as I do a
> >>>>>> lot of rsyncing/rdiff-backup:ing and similar stuff (with many
> >>>>>> files / large files) on ZFS without any stability issues.
> >>>>>> Problems for me have been limited to 32bit and the memory
> >>>>>> exhaustion issue rather than "hard" issues.
> >>>>> It's not generally true since kmem problems with rsync are often
> >>>>> hard to repeat - I have them on one machine, but not on another,
> >>>>> similar machine. This nonrepeatability is also a part of the
> >>>>> problem.
> >>>>>
> >>>>>> But perhaps that's all you are referring to.
> >>>>> Mostly. I did have a ZFS crash with rsync that wasn't kmem
> >>>>> related, but only once.
> >>>> kmem problems are just tuning.  They are not indicative of
> >>>> stability problems in ZFS.  Please report any further non-kmem
> >>>> panics you experience.
> >>> I agree that ZFS is pretty stable itself. I use 32bit machine with
> >>> 2gigs od RAM and all hang cases are kmem related, but the fact is
> >>> that I haven't found any way of tuning to stop it crashing. When I
> >>> do some rsyncing, especially beetwen different pools - it hangs or
> >>> reboots - mostly on bigger files (i.e. rsyncing ports tree with
> >>> distfiles). At the moment I patched the kernel with
> >>> vm_kern.c.2.patch and it just stopped crashing, but from time to
> >>> time the machine looks like beeing freezed for a second or two,
> >>> after that it works normally. Have you got any similar experience?
> >> That is expected.  That patch makes the system do more work to try
> >> and reclaim memory when it would previously have panicked from lack
> >> of memory.  However, the same advice applies as to Ivan: you should
> >> try and tune the memory parameters better to avoid this last-ditch
> >> sitation.
> > 
> > As Ivan said - tuning kmem_size only delay the moment system crash,
> > earlier or after it happens - that's my point of view.
> So the same question applies: exactly what steps did you take to tune 
> the memory parameters?  Extracting this information from you guys 
> shouldn't be as hard as this :)

I was playing around with kmem_max_size mainly. I suppose messing up
with KVA_PAGES is not a good idea unless you exactly know how much
memory you software consume...
regards, Maciej Suszko.

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