need help with ZFS

Kip Macy kmacy at freebsd.org
Mon Aug 31 21:51:10 UTC 2009


>> vm.kmem_size="1536M"
>> vm.kmem_size_max="3072M"
>> vm.pmap.shpgperproc="1024"
>> vfs.zfs.arc_min="256M"
>> vfs.zfs.arc_max="384M"
>> vfs.zfs.vdev.cache.size="50M"
>> vfs.zfs.prefetch_disable="1"
>> kern.maxproc="20000"
>
> Since FreeBSD 7.2 no additional ZFS tuning in loader.conf is needed (on amd64).
> You should remove all those settings from loader.conf, reboot, and re-run the tests.
> Maybe, just maybe you get a panic just because of those settings.

Actually you probably still want to set kmem_size, kmem_size_max, and
arc_min. kmem_size_max just overrides auto-tuning it doesn't actually
raise kmem_size. I have found that the ARC can get starved out by user
processes with many pages in the page cache so a large arc_min can be
useful too. Bear in mind that kmem_size can safely be much larger than
physical memory, kmem_malloc can often fail due to KVA fragmentation
even when physical memory is plentiful.

 -Kip


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