Complex sentence: Large, sequential I/O operations are left to be performed by the origin device, since HDDs tend to have good bandwidth; contiguous I/O operations are tracked internally, so they can be routed around the cache.
Split into simpler sentences: Large, sequential I/Os are left to be performed by the origin device, since HDDs tend to have good bandwidth. Contiguous I/Os are tracked internally, so they can be routed around the cache.