> Don't know anything about how rf works, but can't you just keep an
> array of bits, one for each stripe (or whatever the smallest unit is
> called), marking if that stripe is clean or not, and then fix the
> parity if it's not marked clean.

you might also be able to use the extent allocator (see subr_extent.c)
for this; it may do a better job since in most cases the clean regions
will be contiguous sets of stripes.

					- Bill