Thanks merchant. However I had already read through the Disk Setup and External Drives articles in that section before posting here and I did not find an answer in either article.
What I'm most interested in is whether my external HDD write speed of 50-90 MB/s will be my bottleneck based on my system.
I did a quick test last night rendering a 0:16 second video file (1920x1080 @ 30 FPS, 20-24MM variable bitrate) onto my 3 different hard drives. Surprise surprise, I noticed absolutely no difference among them: all took exactly 0:30 seconds to render regardless of HDD.
With these results I'm inclined to conclude that my render speed is below 50 MB/s, and therefore none of my 3 HDD options would be a bottleneck and I would be free to choose among them.
Adding that third drive will only improve performance over using just two.
Surprise surprise, I noticed absolutely no difference among them: all took exactly 0:30 seconds to render regardless of HDD.
That is no wonder. Your test is only 16s @ 24 Mb/s, so only 48 MB needs to be written. That is done in less than a second, especially if you take into consideration the cache on-board the disk.
If you would test it with a 37 GB file, then the difference would be noticeable. In that case the writing to disk would take around 660 sec. on the external, around 250 sec. on a single dedicated internal disk and only 22 sec. on a superfast large array.
But what is that in comparison to the bulk of the work? Negligent.
You spend say one week editing, two hours transcoding the final results, and need say 10 minutes to write the results to disk. You have to ask yourself if the shaving off, of say 5 minutes is worth the investment.
Very good point. Compared to the amount of work spent on editing, the final step of rendering/exporting is so insignificant. Thanks for your help