On Thu, Jan 18, 2001 at 03:20:34PM +0100, Johan Danielsson wrote:
> Greg Oster <oster@cs.usask.ca> writes:
> 
> > There are some serious consequences to doing *ANYTHING* to data on a
> > RAID set before the parity rewrite completes.  If the parity is not
> > correct for a given stripe, and you write real data to a portion of
> > that stripe, old (and *incorrect*) parity will be used to create the
> > new parity, and that new parity will also be *incorrect*.
> 
> Shouldn't the correct parity be calculated on demand then? That is,
> fix the parity of the stripes you write to, before you write to them.

Seriously!  This is what all hardware RAID controllers I'm aware of do.