just found another image as example
humm, looks weird, but might be functional
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That may be a viable option as it gives 1 SATA port (powered) + 4 USB ports. I don’t like the 7 port USB add on because it leaves you only 8x USB 3 and still gets its USB from the Pi’s USB. It’s not powered and relies on the GPIO for power only, not the best idea.
I’m using this hub.
https://www.amazon.com/Sabrent-Aluminum-Switches-Included-HB-PU16/dp/B07KHRLSTT
With two (3 soon) of these 5 bay enclosures
Both plugged into the 16 port hub and the hub going into one of the USB 3.0 ports on the Pi
Very expensive if you ask me…
Would be interesting to attach a SAS HBA with one or more disk enclosure(s).
what are your plot reading times?
do you get under 5secs?
I have a SAS/HBA setup on my main plotter too. I know they’re pricey but they are rock solid. Plus I bought them very early on before I knew what I was doing 
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Yes. Well under 1 second average.
not bad
for a connection through a dock station and a usb hub, is pretty decent
Yes, it connects in a tree form. But as I have suggested, don’t buy the powered hubs to use with the Pi ever as it could back-feed its power to the Pi and causing the Pi unable to boot/reboot.
Yes, I can see where your issue is coming from.
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It’s a powered USB hub. It will definitely back-feed its power to the Pi and causing the Pi unable to boot/reboot. In fact, this was reported in the user review on its Amazon page.
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It doesn’t tell you what controller chip it’s using and also how many chips it’s using to manage those connections. You better buy a smaller hub and get a lot of dedicated controller chips and it’d be a lot cheaper also.
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It uses a switch to manage the connection which can be buggy at times. This also has been reported in the user review on its Amazon page. You better stick with a simple plug and play hub.
@kreaninw Thanks for the warning. Pretty sure the back-feed problem depends on the USB hub. I’m using a powered USB hub, with no back-feed (I checked with a multimeter). Pi works fine. Would have to check this with each USB hub I guess.
@69chargr The 16-port Sabrent hub looks ideal, but does seem overpriced, then again I won’t be upgrading to a 16 port hub anytime soon! I wonder what the issue is when connecting more than 10 drives… could it be a power supply issue? USB hubs powered with separate supply? Powering them all on at the same time or staggered?
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Sure its from the 16 port usb hub? Was looking through the reviews on the same page posted but it was referring to the 4-port version.
I don’t know. However, this should tell you that the problem exists. Therefore it is better to avoid any unnecessary issues that could happen with the powered hub.
Anyways, I just ordered a USB 3.2 hat for the Pi to see if that helps. If it doesn’t, I am just going to use it for other projects because it is still an amazing little device. I could see purchasing a few more just to have around when an idea pops into my head. 
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Hey everyone. Did anyone manage to connect more than 20 USB devices in a Raspberry Pi 4 8gb already? Or did anyone find any issues while trying it?
I am at 19 HDDs connected with zero issues.
I will also install chiadog today to see I really have zero issues running it. And I will report back again.
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Wouldn’t you save a lot of power if you used larger capacity drives? i.e. one drive of 12tb instead of two drives of 6tb?
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Unfortunately, at the time I bought the drives, there’s a selling limit of how many drives one consumer can buy. Only 6 TB or below drives didn’t have this limitation.
Moreover, even if I bought 12 TB or bigger HDDs to use in the farm, the cost per TB of the bigger HDDs would be a lot higher (2-3 times higher) than the smaller HDDs, thus made no sense to go for bigger drives to save the little cost of power that I could have saved.
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Assuming same manufacturer/all things equal; - bigger drives consume slightly more power - need to spin more platters, and move heavier R/W heads. Not sure how much more exactly, but is not as simple as being twice as efficient to go twice as large.
With external drives the best power saving measure would be to make sure you’re not running one low quality power supply per drive - if you can, you want to use a single better rated power supply with a distribution cable assembly/board.
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Turns out things aren’t so simple, after looking at some data sheets, date of manufacture comes into play. 12-18TB drives made in 2021 are much more efficient than 1-8TB made in 2017.
Even in the same lineup and year of manufacture, larger drives can be slightly more energy efficient than smaller drives.
Seagate Ironwolf Nas Drives
| Model Name | Capacity | Model No. | Avg | Idle |
|---|---|---|---|---|
| Ironwolf Nas | 12TB | ST12000VN0007 | 7.8W | 5.0W |
| Ironwolf Nas | 6TB | ST6000VN0033 | 8.1W | 7.2W |
Seagate Baracuda Pro Drives
| Model Name | Capacity | Model No. | Avg | Idle |
|---|---|---|---|---|
| Baracuda Pro | 12TB | ST12000DM007 | 7.8W | 4.83W |
| Baracuda Pro | 6TB | ST6000DM004 | 9.0W | 7.2W |
Western Digital - Gold Enterprise
| Model Name | Capacity | Model No. | Avg | Idle |
|---|---|---|---|---|
| WD Gold Enterprise | 12TB | WD121KRYZ | 6.9W | 5.0W |
| WD Gold Enterprise | 6TB | WD6003FRYZ | 7.0W | 5.9W |
Refs:- IronWolf Nas Datasheet, Baracuda Pro Datasheet, WD Gold Datasheet
If this data holds true in real-world usage, then using two 6TB uses slightly more than twice the power of a single 12TB drive.
While not definitive, the notion that larger drives consume more power than smaller drives isn’t necessarily true. Who knew?
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