I cut the hash database into 256 pieces based on the last two digits of hash so chunk is smaller than 1MB. To check one password it only downloads one piece. So hopefully it won't be that bad.
Assuming the split is computer-generated based on a parameter, why not use the last three digits and cut it into 4096 pieces, where each chunk is under 64KB? If your bandwidth bill is small it won't matter (ie: not worth the time involved) but if you get a bunch of traffic your cost is 1/16th of what it would have been. Also, to the user the site will be way more responsive as the download will happen quicker.
