> Drive caches are a small factor in comparison. We didn't really even used to worry, or even thing about them.
They used to be small. They've grown approximately at the same speed as HDD sizes, which is significantly faster than throughput, not to mention seek time.
A consumer HDD from c. 2000 might have a 2 MB cache and 40 MB/s throughput, so a full cache empties from sequential data in 50 ms best case. Current 2-3 TB drives have a 64 MB cache and 100-150 MB/s throughput, so a full cache takes around 500 ms minimum to empty.