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AndrewT 20th January 2012 11:04 AM

usb 3.0
Maximum External Data Transfer Rate 640 MBps (5 Gbps)
extracted from:
Buffalo 1TB DriveStation Velocity USB 3.0 External HDD Hardware Encryption

Is this external transfer speed the equivalent to one uncompressed music CD in 1 second?

Can we expect to achieve maximum or near maximum speed in actual operation?
What are reasonable expectations for transfer speeds for USB 2.0 & USB 3.0?

gk7 20th January 2012 11:23 AM

It´s bits not bytes. USB 3.0 will be approx. 60 MB/s

AndrewT 20th January 2012 11:25 AM

It states both bits (b) and bytes (B)

gk7 20th January 2012 11:46 AM

Sorry, yes you´re right, it is really bytes, USB 2.0 is about 60MB/s.
So yes this would be equivalent to one uncompressed music CD in 1 second.
I have not used USB 3.0 myself yet, but Wikipedia says that "...this speed is typically only achieved using powerful professional grade or developmental equipment."
USB - Wikipedia, the free encyclopedia

necplusultra 20th January 2012 11:52 AM

at v7200 rpm. is there not a seek time bottleneck there? The port can take the throughput but can the HDD feed the port at that speed.

theAnonymous1 20th January 2012 03:14 PM

Not going to happen with a spinning disk. Modern consumer SSD's can't even reach 640MBps; the good ones average around ~550MBps.

I think the transfer speed claim on the external drive is just a clever marketing gimmick. I would assume they mean the data from the tiny 16MB buffer can potentially be sent that fast.

theAnonymous1 20th January 2012 03:18 PM

Yup, buffer to USB interface....

"External (Interface) Transfer Rate

The internal transfer rate of the drive represents the speed with which bits can be moved to (from) the hard disk platters from (to) the hard disk's integrated controller. The external or interface transfer rate represents the speed which which those bits are moved between the hard disk and the rest of the PC. This is usually faster than the internal rate because it is a purely electronic operation, which is typically much faster than the mechanical operations involved in accessing the physical disk platters themselves. This is in fact a major reason why modern disks have an internal buffer."

PCGuide - Ref - Transfer Performance Specifications

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