The real problem with this error message is that the kernel is braying
about a temporary error that it recovers from. I've been seeing this
on a DigitalServer 3305 (nee AlphaServer 800 5/500; a 500 MHz 21164a
system, originally with 500MB RAM, now with 2GB RAM) running NetBSD
3.1 for some years now - my primary NFS server. It first showed up
when I created an FFS on a striped CCD with 64k blocks, and reducing
to 32k blocks didn't help.
My read of the code involved is that the isp(4) driver is making a few
too many requests of the bus_space or bus_dma code when I/O piles up
(forgot which - I looked a very long time ago), and doesn't back off.
I see these every day with CVS updates.