need help with ZFS

[Kai Gallasch]

On Sat, 29 Aug 2009 18:00:37 +0200
wrote Pawel Jakub Dawidek <pjd at FreeBSD.org>:

> > bonnie++ -s17000 -d. -n128
> > 
> > for about 10 minutes:
> > 
> > http://omploader.org/vMjg5aQ/IMG_0057.jpg  
> [...]
> 
> I'm running your test on pretty low-end h/w (i386, 1GB of RAM, two
> cores) and cannot reproduce the problem for few hours now. The only
> tuning I did was to set vm.kmem_size to 1GB. You still need to do
> this very tuning even on amd64.

Hi.
Could you give a short explanation why on amd64 it is still necessary
to set vm.kmem_size to 1GB ? I thought with zfs on FreeBSD-7.2-STABLE
tuning kmem was not necessary any more.

The reason I ask is, I have some servers on FreeBSD-7.2-STABLE
AMD64 that are quite stable, but sometimes suffer from zfs
performance degradation when zfs is competing with applications using
huge amounts of RAM. Those servers are not swapping at all when this
takes place.

--Kai.