Exporting to an external HDD USB 3.0 (2.5" disk)

Question

Hello,
I just recently built a new rig and I currently have two internal hard drives:
Toshiba Q-Series SSD 256 GBBoot, Programs, Media Cache
Seagate 7200 RPM 1TBMedia Files, Project Files
Reading through these forums I saw recommendations to use a 3rd drive in order to avoid reading/writing to the same drive at the same time.
I have an external HDD (WD My Passport 2TB) that I'm guessing spins at 5400 RPM due to its 2.5" size. It's connected through USB 3.0. I tested read/write and it starts around 90 MB/s, then drops down to 50-60 MB/s after a few minutes.
If I'm doing light editing (~5 minute clips) would this external HDD be my bottleneck? And will I see a significant improvement by buying a new 7200 RPM internal drive?
Other specs:
CPU:  i7 4770k @ 4.4 GHZ
GPU:  Radeon 7950 @ 1000 base, 1450 memory
Mobo:  Asrock Z87 Extreme4
RAM:  32 GB Kingston HyperX @ 1600 mhz 10-10-10-27 timings
Thanks!

Answer 1

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.