I just thought I'd add my comments to this list:

> When I was investigating this previously, I had determined that all of the
> following were factors conducive to causing the problem:
>
> - Low system memory. My main system has only 128 MB RAM, and usually
runs about 60 MB into swap.
> - Large SU/chunk sizes.
> - softdep.
> - More columns in the RAID5 set.
> - swap on RAID5.

My system presently has 512Mb of memory, so I guess this has something to
do with the added disk io that comes with swapping on the raid array. I'm
now running your suggested hacks in rf_netbsdkintf.c and have
increased uvmexp.reserve_kernel to 192. This alone didnt make the system
rock solid, so I also increased vm.kmempages from 32k to 64k, and added
"options RAIDOUTSTANDING=3". With these mods, my system seems to be stable
even during heavy disk usage. This is probably not a "clean" way to solve
the problem, but it works. Noone would be more happy than me if Raid5
would work with a vanilla kernel, but we can only hope that Greg Oster
will have time to work with it. :) I will try to help in any way I can.

// Thomas Hertz