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Speed of 2.5" HD: External USB3 vs. Internal SATA

Last response: in Storage
January 27, 2013 10:28:51 AM

I am trying to find information on the relative "performance hit" which would be taken by using an external USB 3 drive instead of a traditional internal SATA HD.

In order to try to evaluate the speed difference, I have looked at the performance charts for the 2.5" external USB3 drive I would be using (WD My Passport) and compared it to the internal SATA drive I would use (WD Scorpio Black).

The Read Throughput Average is 83.5MB/s for external against 97.99MB/s for internal.

The Write Throughput Average is 83.3MB/s for external against 93.42MB/s for internal.

The difference in these figures is approximately 20%, am I right in thinking that the actual difference in performance would only be around 20%? I am aware that I am overlooking factors such as read access time, performance reading smaller files etc, does anyone know the relative difference these would make?

The reason why I ask is because I am building a system using Akasa Euler case, this case only has room for 1 internal 2.5" drive. The MOBO does support mSATA, I was originally planning on going with an mSATA 256GB SSD along with the 750GB WD Scorpio Black.

However the mSATA is only 3.0GBps, so I would sacrifice SSD speed against using a Samsung 840 Series 250GB SSD (can use SATA 6.0GBps). However using a traditional SSD would mean there is no space for the 750GB WD, meaning I would have to rely on an external USB 3.0 drive. :( 

What would other people choose to do in this situation? Changing the case is not an option, I am hellbent on using this one.
a c 99 G Storage
January 27, 2013 1:20:17 PM

While the numbers might seem fairly close, in reality there would be a larger performance difference than that in real-world scenario's.
USB and SATA controllers are optimized for different workloads.

Running a test right now on a USB3 external drive (WD My Passport 500GB) and a Seagate Barracuda 1TB 7200RPM drive, will post the Crystal Disk results at the bottom. The test is a bit biased toward the internal drive since its 3.5" and isnt as full as the external, but even so the performance difference is fairly large.

That being said, if all your storing on this drive is music, movies and just general files. Not running games/programs or using it as a render output drive, then performance shouldn't matter really.

My suggestion, see if you can actually fit the drive in there anyway. Might require a bit of thinking and some modifications to the case, but there must be a way.
Or take advantage of the e-SATA port that is most likely on the back of the mobo. That will allow you to plug in SATA devices as long as you have some external method of giving it power.

EDIT: Forgot to actually post the results :p 
Left is the internal drive (Seagate Barracuda 1TB 64MB cache 7200RPM, on a SATAIII connection) and the right is the external (WD My Passport 500GB USB3, connected by USB3).