Not much explanation needed, question is exactly what the thread title says. I have a handful of large 5TB to 10TB external HDDs, all of which are either USB 3.0 or USB 3.1. Most are either at or nearing capacity, I use them for archiving files that I either don't need to access often, or don't need to store on my internal drives. The main issue is that both reading and writing to these drives has become somewhat slow, much slower than USB 3.x speeds. Obviously writing will become slower since there is very little available space. And each of these drives have native NTFS compression enabled (not really necessary, but it helps to squeeze out all the capacity I can get), which does slightly decrease speed (not significantly, in my experience, but it depends on the drive). But when they were empty the read/write speeds were much faster.
This has led me to believe that maybe defragging to consolidate fragmented files might help. Of course, this won't increase available space. And if a crash or some other error occurs during the defrag, that could mean corruption of data that was otherwise OK before. So...is it safe? Or should I just leave it alone?