ZFS on a notebook/512M settings

[Craig Boston]

On Thu, Jul 26, 2007 at 12:52:33AM +0400, Dmitry Morozovsky wrote:
> I want to join the 'eating our own dogfood' company using ZFS on my notebook. 
> However, it is armed with only 512M of RAM.  What are tunings which would 
> possibly keep it from panicing? For now, I've got in /boot/loader.conf:

I'm using

/boot/loader.conf:
vm.kmem_size="268435456"
vfs.zfs.prefetch_disable="1"

/etc/sysctl.conf:
kern.maxvnodes=22500

on my home fileserver with 512MB of RAM without incident.  It does
a lot of small file access -- cvsup's RELENG_4, RELENG_6, and HEAD
sources nightly and imports them into subversion.

You could probably bump up maxvnodes a little without it panicing.  I
started conservatively and performance has been acceptable so I haven't
taken the time to tune it fully.

I've seen recommendations on the BSD lists to use zil_disable to avoid
low-memory deadlocks (which I've not yet encountered).  I've also seen
dire warnings on the OpenSolaris lists about possible data corruption if
you disable the ZIL, so I'm unsure about that one.  For now I'm erring
on the side of caution and leaving it enabled until it causes me
problems.

Craig