How many external HDDs can you have in a Raspberry Pi 4 8gb?

Hello guys. I’m about to buy a Raspberry Pi 4 to be my farmer/harvester. I read a few people saying it can support up to 32 USB devices, but I wanted to confirm with people that already use it if this is true. How many external HDDs are you being able to store in your Raspberry Pis?

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I am currently running with 13 HDDs on the Pi without any issue. And I am farming on both HPool and Flax. CPU usage is around 30% at most while RAM usage never goes above 3 GB from 8 GB that I have.

I am going to end up at 32 HDDs per Pi also. I think the only limitation would be the USB 3’s connection speed which is 5 GB/s. And please note that both USB 3 ports on the Pi shared the same line of connection. It means that you will only get 5 GB/s maxed from both of them. They will not give you 10 GB/s (5 GB/s from each) at any time.

If your HDDs have a maximum read/write speed of 150 MB/s, that will be 33 HDDs in total to reach 5 GB/s.


can you share with us the full details of the rig ?
the cards, power, cables and all ? many peoples look for cheap solution like using the Pi but they cant figure out how to setup the rig and what to buy ?

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  1. Raspberry Pi 4 B 8GB board.
  2. The official case with the fan.
  3. The official HDMI cable (only use for setting the Pi up, then run headless with RDP).
  4. The official power adapter.
  5. SanDisk Extreme Pro 32 GB microSD card (for the OS - Ubuntu 21.04).

I am opening mine 24/7 without any problem and without any air conditioner, 30 C ++ room temperature.

Please note that, do not buy the powered USB hub to use with the Pi as the hub could back feed its power to the Pi and causing the Pi unable to boot/reboot. Since you will most likely connect the Pi with a lot of desktop external HDDs that come with a separated power supply, all you need is the unpowered USB hub. And also make sure you choose the hub with a good USB controller chip (USB 3.1 Gen 1 or above, for instance, VL817 or GL3520).

Also, if you want to remote your Pi from time to time over the internet (when you are outside). You can use VPN + dedicated IP for that (I recommend PIA).


Please keep us informed, how many u can actually connect.
I think i’ve read 13 here before, but nothing near 33.

I dont expect CPU or RAM to become a problem, but the Usb-controller.
Would be rly cool if ur recommended hub-chip allows more than 16 drives.

Also, i wanna add, that my farming response-times increased on my pi with each added drive, but im only at 5 drives yet :sweat_smile:

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I am hitting 15 today and still going for more. I have no issue yet :joy:

I use five 7 ports USB hubs. They are around $7 each which is cheaper than anything you can com across with the powered USB hubs. It’s also a lot cheaper than the HDD enclosure or dock per port/bay/dock.

I will update again when I reached 32 HDDs connected to the Pi.


I run a small pi harvester (2 Drives)… and I question if it makes sense to buy a Pi for this project or if it would be better to dig out a old laptop, install linux on it, and run it as a server. An old laptop would probably be better economy. Food for thought.

The only 32 drive pi set up i’ve seen runs on a ‘rock pi 4’. I havn’t see anyone run a 32 drive rig on a regular raspberry pi yet, but its probably achievable. You’ll also need a beefy 12v PSU to run the 3.5" drives, and powered 16 port USB hubs to run the USB adapters, a cooler for the pi etc.

Some other things to consider is that you’ll need to be pretty familiar with linux to get this working, be comfortable with shucking drives, or spend extra money on compatible SATA to USB adapters (Pi’s don’t play well with some JMicron adapters, and they’re the cheapest ones). Edit: Ok, techinically theres no reason to shuck drives for this project…

I think a 32 drive pi project is cool… but i’m still on the fence about how economical or practical it is.

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That’s nice, keep us updated. If the raspberry pi 4 is able to farm with all 32+ HDDs I think would be the best economical way to have a farm, because of the low energy consumption of the rasp pi.

Also, the computer I’m using for farming (motherboard x570 asus tuf gaming) only recognizes up to 36 USB devices due to the limitation of the XHCI lanes it has. I’m thinking about disabling XHCI (USB 3.0) and using only EHCI (USB 2.0) to try to cheat this limit, but this is looking more complicated than expected, so if the Raspberry Pi 4 works it would be really great.


I am at 15 now and counting. I add 1-2 HDDs to it per day. I still have zero issues, even when I farm 2 chains at the same time, Chai with HPool and Flax solo (I already got 4 Flax).

And yes, due to the very limit of the USB connections on a single board, I didn’t want to waste one for SSD as there are almost zero read/write operations from the OS partition while framing. MicroSD is not fast indeed, but it’s still on par with modern typical HDDs. I also want to see an endurance of the Extreme Pro first and if it’s not working (died young), I will change to their Max Endurance card which could live up to 13 years of 24/7 operation considering it is a lot cheaper than the cheapest SSD anyway :sweat_smile:

IMO, Pi 4 B 8GB is the most economical way to farm electricity wise. It’s also a lot cheaper to buy external HDDs + USB hubs combo than internal HDDs + enclosure bays or even docks of any kind.


I can’t get my Pi 4 8gb to reliably connect even 10 USB drives. I tried both Ubuntu and Raspbian. 8 seems to work just fine, anything above that is extremely unreliable and it apparently crashes the USB controller as the keyboard and mouse stop working as well.

You may need to invest in the USB hat that plugs into the GPIO header and adds additional USB and a 2nd USB chip. That said, you won’t get many more USB drives, even if the USB HDDs are external powered and the hubs are external powered.

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What USB hub are you using? What is its controller chip?

I am using 5 USB hubs (7 ports each) meaning that I got 5 dedicated controller chips. I’ve never had any issue with the connection.

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Not true. You have 5 hubs that share the USB host controller on the Pi. A hub doesn’t have its own dedicated USB controller per say. It’s merely a dumb splitter.

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My hub uses VL817 chip, the same chip that’s being use in the hat you suggested. Therefore it’s not just a mere splitter.

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That part mentioned is merely a “USB hub controller chip”. That is NOT the same as a USB host/interface controller. On a PC or Mac, you only get 1 USB host controller. PCs get the benefit of controllers on PCIe cards.

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That part mentioned is merely a “USB hub controller chip”.

Then, why did you suggest the USB hub hat for the Pi as it also has the same USB hub controller chip?

Nonetheless, I believe that we weren’t talking about the benefit of framing Chia on PC/Mac. However, we are talking about the benefit of farming on the Pi in which the connection with a lot of HDDs shouldn’t be the issue.

If you buy a good hub and get a good chip, it doesn’t matter how many host controllers you get on the Pi. The hub will manage the connections then send them to the host. Therefore as long as the data rate does not exceed the amount supported by the host, you won’t have any connection issue.

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I did not look at it specifically for the controller chip (not host chip). My bad. I made a mistake.

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Im curious as to how these are all connected, it is in a tree form?
Hub 1 to the Pi? Hub 2-5 connected to Hub 1? All powered usb hubs?

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im wondering if anything like this would work to connect HHD’s



Is it weird that I want this? Hahaha

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