Why USB 2.0 HDD is slower than internal drives?

[Mutant_Guy]

My friend had a USB 3.0 external drive and the transfer speed was on my PC (USB 3 port) 32mbyte/s Since it is a HDD it won't make a real different between USB 3.0 and USB 2.0. USB 2.0 support 480mbit/s that is 60 mbyte/s. My question is why fixing that hard drive internally working faster than using on the usb port?

I need a secondary drive i thought to buy a external drive instead of plugging internally.
* Less noise
* Less power
* Less heat generation.
* Also i don't need that drive to be connected always.

But i'm worried about loosing transfer speed because of connecting via usb port. I know sata bandwidth is higher. But any way usb support at least 60mbyte per seconds. So why we are getting low speed on usb compared to sata on the same hard drive? May be the controllers are bad in enclosure?

 

[ThomasJ93]

The 480Mbit/s of USB 2 is a theoretical maximum. In real life scenarios you will almost never reach these speeds.

One of the reasons that internal SATA is faster than USB, is because there's less overhead of the USB controllers. The internal SATA can communicate directly with the chipset and will get you the most performance.

 

[Quaddro]

Since it is a HDD it won't make a real different between USB 3.0 and USB 2.0

well, between usb 2.0 and 3.0 is very different in term of transfer performance

usb 2.0 has maximum signaling rate of 480 Mbit/s and effective throughput up to 35 MB/s or 280 Mbit/s
usb 3.0 has maximum signalling speed of 5 Gbit/s and effective throughput up to 512MB/s or 4Gbit/s

By the way, all the number above is theoritically. That's means, for real application, there's none of gagdet (including hdd) in the market will work in that number.

USB 2.0 support 480mbit/s that is 60 mbyte/s
But any way usb support at least 60mbyte per seconds

That's impossible for usb 2.0 hdd reach 60mbyte/s.

Yes, usb 2.0 support 480mbit/s (60 mbyte/s), but it works for two way transfer speed. one way from your computer to your gagdet, and another way from your gagdet to your computer.
that why effective throughput up to 35 MB/s or 280 Mbit/s for single way application.

if you wanna take some serious speed, then take usb 3.0 hdd.

compared to sata on the same hard drive?

sata 2 has full 3gbit/s speed
sata 3 has full 6 gbit/s speed

of course, it will smoke any usb interface speed available right now.

 

[Hawkeye22]

Also, USB is a shared bus. The more USB devices that are plugged in, the less bandwidth is left for other devices. SATA is a dedicated connection.