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Assuming unlimited drive speed, what's the limiting factor in transfer speed?

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#1 corrado33


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Posted 03 October 2016 - 10:40 AM

I recently learned that WD external (aka "My Book" drives) use some sort of proprietary format so that their drives can't be removed from their exclosures and used without a reformat. So that led me to transferring a few terabytes of data off of my multiple mybook drives onto internal drives, so I could put the (often knocked over and really BRIGHT) external drives inside my machine. (And to clear up a bit of space on my surge strips...)


Unfortunately, one of the drives was USB2 only (ok it had firewire, but who has firewire on their PC anymore? I had it on my mac all the time but I don't have macs at home anymore. 


Anyway, the USB2 transfer capped at 35 MB/sec, as expected. The USB3 drive capped at ~120 MB/sec, also expected (but for different reasons.) USB3 transfer speeds exceed the read speed for the 5400 RPM sata drive inside the enclosure... right?


Anyway, it got me wondering... What's the limiting factor for transfer speed assuming unlimited drive speed on both ends (infinite raid0?) Is it software? Is it hardware? I guessed the latter, hence why it's here. 

Edited by corrado33, 03 October 2016 - 10:42 AM.

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#2 dc3


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Posted 03 October 2016 - 02:56 PM

External hdds have extra circuitry which converts the SATA or IDE interface to a USB interface.  If you have a internal USB port you should be able to connect the hdd to it to power it.

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#3 Gorbulan


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Posted 03 October 2016 - 03:59 PM

The limiting factor is the USB interface, so hardware. 

#4 cat1092


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Posted 04 October 2016 - 12:26 AM



Unfortunately, one of the drives was USB2 only (ok it had firewire, but who has firewire on their PC anymore? I had it on my mac all the time but I don't have macs at home anymore. 


Just in case you may want to know, you can purchase a USB 3.0 drive enclosure, though to be honest, the quality 3.5" models constructed of aluminum or metal will cost almost as much as some 1TB HDD's on promo at Amazon. 2.5" models are much less expensive & can be found on eBay for as little as $8 (metal with leather pouch & USB 3.0 cord). 


However, if it's transfer rates you desire, connect to an extra SATA port in the PC, it'll be faster than either USB 2.0 or 3.0, and a few has stated that 3.1 cards doesn't transfer data as fast as advertised. So unless you have M.2, then SATA is your fastest medium of internal storage. If by chance you're using it as a backup drive internally, be sure to disconnect the power & data cables after backup is complete. Otherwise, if a nasty Malware sneaks in, some can encrypt your backups, rendering these useless. Leave the case open as a reminder to disconnect when finished, and be sure to wear a ground strap, with the alligator clip connected to the steel frame of the case or drive bay, or touch the metal case for ground during plugging/unplugging for safety. :)



Performing full disc images weekly and keeping important data off of the 'C' drive as generated can be the best defence against Malware/Ransomware attacks, as well as a wide range of other issues. 

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