How many externals to a USB hub
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I have 5 on a powered USB hub and really don't see any performance hit. But as @Hitti2 points out, there is only so much bandwidth, so I am sure there is a point where performance will degrade.
The real pros can probably tell us the preferred maximum per USB card/interface (I have 2 usb 3.0 cards installed in my system 3 drives on one, and 6 total on the other)
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It depends on several factors, but generally, in order to get the best possible read times from my Seagate backup plus 8TB drives, I don't wish to connect more than three in a USB 3 hub. The hub itself does not need to be powered if your drives have their own external power supply.
When mining multiple drives, you will most likely reach a bottleneck in the bandwidth of your USB 3 host controller. Theoretical max speed of one USB 3.1 gen 1 host controller is 625 MB/s, but I have been told 320 MB/s is a more likely number. When we mine our plots, we only need to read one scoop out of 4096 each round, which represents 0.025 % of the total size of plots. So, if we have 50 TB of plots (50 000 000 MB), we only need to read 50 000 000 x 0.00025 = 12 500 MB in one round.
12 500 MB per round / 320 MB/s (controller likely speed) = 39.0625 seconds. Total round time of about 39 seconds can be improved by dividing the HDDs onto multiple USB 3 host controllers using a dedicated USB 3 multi controller card (such as this one: http://www.sonnettech.com/product/allegroprousb3pcie.html). Read speed will also be impacted by the read speed of the HDDs themselves, as well as CPU/GPU/motherboard.
Conclusion: If you don't care about fastest possible read times, buy a 10-port USB 3 hub. If you do care, go with small hubs so that you can get the most out of your USB 3 host controller, and preferably get hold of one of those multi controller cards I linked to.
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3 Replies
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@Propagandalf
Good point, all my externals have their own supplyI think I'll get an unpowered 10port, an only connect 3 or 4 at first and see how much of a difference there is each time I add one
My laptop has four 3.0 ports, so I plan to "max" them out before I buy a dedicated machine just for BURST-ing
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@mrgoldy Sounds like a good plan! Since you're on a laptop chances are big that all your four USB 3 ports route back to the same USB 3 host controller, so basically they're the same as a hub. Unfortunately, that card I linked to is meant for desktops, but I think there are ways of upgrading laptops with more host controllers as well.
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It looks like I have 2 Host Controllers, maybe 3?
Or is the 3.0 the only one? and the others above it are 2.0?
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@mrgoldy The enhanced controllers are USB 2, whereas the extensible is USB 3 :) You should be able to tell the diffence when you look at the ports. USB 3 ports are usually blue colour, or red, like on my laptop.
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2 Replies
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@Propagandalf
all 4 of 4 ports are blue, that's why I'm a little confused
ASUS ROG G750JW in case you're wondering
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@mrgoldy Hmm... strange, maybe there are some internal USB 2 connectors for legacy compatibility or something like that, that you can only access by opening it up. Or maybe they are connected to some other bus through a different type of connection on your laptop. I really couldn't tell you, but you will notice a big difference in speed from USB 2 to USB 3 when mining. :)
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This post is deleted!
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@Propagandalf said in How many externals to a USB hub:
It depends on several factors, but generally, in order to get the best possible read times from my Seagate backup plus 8TB drives, I don't wish to connect more than three in a USB 3 hub. The hub itself does not need to be powered if your drives have their own external power supply.
When mining multiple drives, you will most likely reach a bottleneck in the bandwidth of your USB 3 host controller. Theoretical max speed of one USB 3.1 gen 1 host controller is 625 MB/s, but I have been told 320 MB/s is a more likely number. When we mine our plots, we only need to read one scoop out of 4096 each round, which represents 0.025 % of the total size of plots. So, if we have 50 TB of plots (50 000 000 MB), we only need to read 50 000 000 x 0.00025 = 12 500 MB in one round.
12 500 MB per round / 320 MB/s (controller likely speed) = 39.0625 seconds. Total round time of about 39 seconds can be improved by dividing the HDDs onto multiple USB 3 host controllers using a dedicated USB 3 multi controller card (such as this one: http://www.sonnettech.com/product/allegroprousb3pcie.html). Read speed will also be impacted by the read speed of the HDDs themselves, as well as CPU/GPU/motherboard.
Conclusion: If you don't care about fastest possible read times, buy a 10-port USB 3 hub. If you do care, go with small hubs so that you can get the most out of your USB 3 host controller, and preferably get hold of one of those multi controller cards I linked to.
Thanks. I use the same drives as you and was going to buy a 50 dollar 10 port powered hub. Still might as it had good reviews but might be overkill link. I have 6 USB 3.0 ports but am currently plotting my fifth drive ;)
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@Propagandalf I have 5 superspeed and one eXtensible so I have 6 USB3.0 controllers correct? Makes sense since I have 6 blue USB ports.
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@mrgoldy said in How many externals to a USB hub:
@Propagandalf
all 4 of 4 ports are blue, that's why I'm a little confused
ASUS ROG G750JW in case you're wonderingMost controllers with 3.0 capability will show the 2.0 ghost ports in device manager or a usb tree viewer for the backward compatibility for 2.0 devices.
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currently run 7 externals through a hub and takes 27 seconds to read almost 30tb around 300 Mb/s
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@newsense2004 said in How many externals to a USB hub:
@Propagandalf I have 5 superspeed and one eXtensible so I have 6 USB3.0 controllers correct? Makes sense since I have 6 blue USB ports.
It is not common to have so many host controllers unless you have installed specialized hardware such as multi controller cards. So, I think superspeed refers to internal hubs or ports, whereas the extensible refers to your host controller. Having blue ports simply means that the port routes back to a USB 3 host controller, and sometimes the ports are red as well.
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in college i found out you can have a maximum of 255 usb devices hooked up to a computer at anyone time.
the thing we plugged into 255 usb ports was a usb humping dog :P
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What about USB 3.1 Gen2 (10gb)? Someone have tested 10 ports usb 3.1 gen2 hub?
