Conceptual questions about device driver

Hi, I have some conceptual questions about device driver : 1. Write order fidelity should be maintained when submitting requests from device driver to disk below. However, acknowledging these requests it is okay if we don't necessarily maintain that order, right? 2. Also i want to understand what the device driver does say if in a multiple paged bio, some of the pages get written and some don't, we send the error in the bio. But what about the pages it has already written??? It can't possibly do anything about it, right? Regards, Neha