USB3.0 and Gigabit switch in NAS system

[mydownload]

Hi! I'm quite curios about USB3.0 and Gigabit switch logics in NAS system.

1. Assuming a theoretical data speed of USB3.0 is 4800Mbps and Gigabit Switch is 1000Mbps. If I buy a USB3.0 hub and plug to 2 of External HDDs with USB3.0 then plug Usb hub to Notebook and transfer data between External HDD. Will the speed share as 4800Mbps / 2 = 2400Mbps/channel?

2. From 1, if I plug off 1 External HDD and re-plug it to Notebook with different USB3.0 USB Controller and tranfer data between External HDD. Will it run at full speed 4800Mbps?

3. If I tranfer data between External HDDs that I plug on my PC and another one plugged to Noteboook which both are on connected to same NAS server, based on the theory it would have 1000Mbps speed, as bottleneck of Gigabit switch right?

4. Assuming I buy a converter from a USB3.0 to Gigabit port(as below link) ,plug External HDD to converter, then put through a Gigabit switch. Will my External HDD be deteced on NAS system?
http://www.uppic.org/image-BB6B_56AB8EF8.jpg

5. Since it's a NAS system. If I transfer data by Notebook between 2 of full 2 TB External HDDs which plugged to NAS server box. It usually may take a whole day. Can I shutdown my notebook while data still tranfering?

 

[dave_the_nerd]

Hi! I'm quite curios about USB3.0 and Gigabit switch logics in NAS system.

Okay, well first off - USB is a master/client system. A single USB controller can access one or more client devices which are owned by that controller/master. It is smart, it does all the thinking, and tells the clients what to do.

USB client devices are stupid. They only know how to take orders from a USB master.

Gigabit Ethernet is networking - it allows any number of computers (which would be "master" devices for USB purposes) to talk to each other.

1. Assuming a theoretical data speed of USB3.0 is 4800Mbps and Gigabit Switch is 1000Mbps. If I buy a USB3.0 hub and plug to 2 of External HDDs with USB3.0 then plug Usb hub to Notebook and transfer data between External HDD. Will the speed share as 4800Mbps / 2 = 2400Mbps/channel?

Yes and no. If you plug two devices into the same controller, you get full speed access to one at a time. If you are talking to one device, you get the 4.8Gbps, even if you have like 100 other USB devices plugged in and not doing anything.

If you are talking to two at the same time, (say, copying a file from one to the other) the apparently speed is 2.4Gbps.

But your hard drives will be much slower than that anyway. (a spinning hard drive is unlikely to push more than 1.5Gbps of data down a pipe, and most are slower yet.)

2. From 1, if I plug off 1 External HDD and re-plug it to Notebook with different USB3.0 USB Controller and tranfer data between External HDD. Will it run at full speed 4800Mbps?

Not sure what you mean, but if you mean what I think you mean, do not try this. A usb hard drive can only be accessed by a single computer at a time. Attempting to violate this will probably corrupt your data.*

*One could theoretically program a computer to operate as a USB hard drive for multiple other usb "masters" and keep the files and file system intact and managed, but at that point, you've basically reinvented a SAN. Some of those USB-sync cables that allow two computers to transfer files over USB basically work this way.

3. If I transfer data between External HDDs that I plug on my PC and another one plugged to Notebook which both are on connected to same NAS server, based on the theory it would have 1000Mbps speed, as bottleneck of Gigabit switch right?

Yes, network connection speed between two computers will bottleneck other faster things.

4. Assuming I buy a converter from a USB3.0 to Gigabit port(as below link) ,plug External HDD to converter, then put through a Gigabit switch. Will my External HDD be deteced on NAS system?
http://www.uppic.org/image-BB6B_56AB8EF8.jpg

No. For several reasons. Put simply, the external HD is a client device, so is the ethernet adapter, and they don't know how to talk to each other.

5. Since it's a NAS system. If I transfer data by Notebook between 2 of full 2 TB External HDDs which plugged to NAS server box. It usually may take a whole day. Can I shutdown my notebook while data still tranfering?

No. USB client devices need masters to think, and ethernet can only provide communication between two "smart" devices.

What is it you're trying to do, exactly - back up 2TB of data every day as fast as possible? You probably just want to implement differential backups.

 

[mydownload]

Woww. Great thanks for your answer, dave_the_nerd

I'm clear on everything now!