Our Iometer benchmark started with static data occupying 50.4% of the drive. Then, we ran a 64 KB-block sequential write across all of the remaining capacity. Performance was reported at 187.74 MB/s.
Next, we deleted the static data and re-ran the test, resulting in 178.67 MB/s.
Finally, we created a partition that left 50% of the drive for over-provisioning and ran the same test once more. Performance clocked in at 327.17 MB/s. Over-provisioning by 50% appears to alleviate any reduction in write speed.