8.1 amd64 lockup (maybe zfs or disk related)

[Jeremy Chadwick]

On Tue, Feb 08, 2011 at 11:43:20PM +1100, Jean-Yves Avenard wrote:
> On 7 February 2011 20:03, Jeremy Chadwick <freebsd at jdc.parodius.com> wrote:
> 
> > They're discussed practically on a monthly basis on the mailing lists
> > (either freebsd-fs or freebsd-stable).  Keeping track of them is almost
> > impossible at this point, which is also probably why the Wiki is
> > outdated.
> 
> I like Sun's take on the matter:
> 
> http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Tuning_is_Evil
> "Tuning is often evil and should rarely be done.
> 
> First, consider that the default values are set by the people who know
> the most about the effects of the tuning on the software that they
> supply. If a better value exists, it should be the default. While
> alternative values might help a given workload, it could quite
> possibly degrade some other aspects of performance. Occasionally,
> catastrophically so.
> 
> "
> 
> Which I thing summarise perfectly ZFS "tuning".
> 
> If you want to know 20 differents opinions on how zfs needs to be
> tuned; talk to 20 different people.
> Everyone has their own ideas on how it should be done ; believe a
> particular setting made things better.
> 
> I tried them all I could read here, none of them make much significant
> difference, and and when they do, usually it's just for the worse.

Sorry, that just isn't the case.  I'm not going to get into an argument
on a mailing list, or privately for that matter, regarding the
implication of *not* adjusting what I've shown.  Even developers who are
commit coding to the ZFS tree -- such as avg@ -- have advocated these
settings.

The documentation you reference is for Solaris and OpenSolaris.  When
was the last time you used either of them?  Part of my day job involves
maintaining and managing hundreds upon hundreds of Solaris 10 servers.
Do they require tuning?  Absolutely not.  And that's because ZFS on
FreeBSD *is not* identical (re: innards, VM, etc.) to that of ZFS on
Solaris.  You can dig up verification of these claims by reading
freebsd-fs and freebsd-stable archives.

If you want rock-solid, no-tuning-needed ZFS, run Solaris.  Period.
I have nothing more to say with regards to this part of the thread.

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP 4BD6C0CB |