Scatterlist chaining

I was wondering, does this mean that the speed of disk I/O (I/O to the raid controller) is
being negatively impacted by this constraint, if we can only transfer a maximum of 800KB per
interrupt. 

This means that either a processor needs to spend more time servicing interrupts, because more
interrupts need to be generated to move the data about, or that less data is going to get
transferred?