3.5 vs 2.5 external hard disk speed.

[smalltech]

Comparing a 2.5 external hard disk (only need to connect to USB cable) vs a 3.5 external hard disk (need to connect to USB cable and need external power supply). Assuming all specs are the same (or very similar) and connecting to a same USB port of a same PC, will the 3.5 be faster because it is powered by external power supply? How much faster would the 3.5 be?

Is it because the 3.5 external hard disk has an external power supply so it is faster?

(update: using 3.0USB )

Thanks

 

[InvalidError]

3.5" HDDs have higher transfer speed simply because the linear speed of the disk surface passing under the drive heads is faster due to the larger diameter.

If you use USB2 though, both will be limited to 40-50MB/s by the USB interface.

 

[Karnivore]

The difference is negligible between the two. I can't wait for USB 3.1 drives though, surprised there's nothing out yet considering the new boards have been released and X99 have revisions for USB 3.1 expansions.

 

[Dragos Manea]

The difference is negligible between the two. I can't wait for USB 3.1 drives though, surprised there's nothing out yet considering the new boards have been released and X99 have revisions for USB 3.1 expansions.

Thats because mechanical drives can not saturate the 3.0 port, usb 3.0 max speed is 5 gpbs or 640 MB/s, no mechanical drives can reach that speed, i'm using a usb 3.0 hub with 4 ports conected to my only port on my notebook, i m using 4 external hdd (i work with very very large special multispectral images, each file has around 15 gb) and all of them working simultaneous keeping stable 90 mb/s (4x90=360 MB/s total out of 640), so on the same port i conected 4 external hdds and i cannot saturate the usb port, why we need an 3.1 external drive? even it is 3.1 certified the real speed will be less then 10% of total port speed. ONly thing that can saturate usb 3.0 and we need a 3.1 is a SSD external drive.

 

[InvalidError]

why we need an 3.1 external drive? even it is 3.1 certified the real speed will be less then 10% of total port speed. ONly thing that can saturate usb 3.0 and we need a 3.1 is a SSD external drive.

That is probably what he meant by wanting USB 3.1 external drives: SSDs, thumb-drives and possibly RAID arrays.

As far as HDD transfer speeds go, my 1TB WD Black can hit 140-200MB/s sequential read/write, so three of them in RAID0 or software RAID1/3/5/6 would get pretty close to bottlenecking 5Gbps which yields only ~500MB/s usable after USB overhead.

 

[Dragos Manea]

why we need an 3.1 external drive? even it is 3.1 certified the real speed will be less then 10% of total port speed. ONly thing that can saturate usb 3.0 and we need a 3.1 is a SSD external drive.

That is probably what he meant by wanting USB 3.1 external drives: SSDs, thumb-drives and possibly RAID arrays.

As far as HDD transfer speeds go, my 1TB WD Black can hit 140-200MB/s sequential read/write, so three of them in RAID0 or software RAID1/3/5/6 would get pretty close to bottlenecking 5Gbps which yields only ~500MB/s usable after USB overhead.

Well that is not so common, 98% of peoples uses only one device on the usb port, not using hubs or raid setups so its not in their economical advantage.