In practice you see noticeable degradation of performance for streaming reads of large files written after 85% or so. Files you used to be able to expect to get

In practice you see noticeable degradation of performance for streaming reads of large files written after 85% or so. Files you used to be able to expect to get 500+MB/sec could be down to 50MB/sec. It's fragmentation, and it's fairly scale invariant, in my experience.