After I started running gmirror and gstripe, I started getting messages
like the following:
ad8: FAILURE - out of memory in start
It occurs on various of the four disks in the system. Once it happened
on all four. I have noticed some data corruption which I was able to
fix from a backup, but I don't really know the cause of the data loss.

I found one message on the internets about setting vm.kmem_size_scale
to 2 -- but can't find any documentation confirming or explaining.

The system is 6.2 prerelease, that I keep updating to try to make the
messages go away. The system is not under heavy load. What's going
on? Should I go back to gvinum?