Technomatic Rescue
I am using a large (although larger would be possible) buffer size of 8MB, and it's reading 1MB worth of data from the disc in a single read operation. So, it should take 8 reads to fill up the buffer, but errors slow the process down considerably.
When the buffer is full, Chunker stops and invites the user to save the contents of the buffer elsewhere. There are too many different saving possibilities for the program to cater for every option, so intead the user gets a command prompt to navigate to a save location and then perform the save manually, so to speak.