How many HDDs can I connect to the Windows 11 operating system?
As many as you can afford presumably?
I’m at 63 on Win11 Pro with no end in sight.
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I thought there were restrictions on the number of HDDs
You can run out of drive letters, but it is better to mount the disks in a folder (like linux)
Most likely that is 128, due to how USB is being handled (i.e., USB controller H/W). However, I am not sure about it.
Another thing is that it may also depend on how old your box is (what are the USB controllers, I guess). I have some old AMD APU mITX, and it struggles around 20-30.
how is it “numbered” in Win? DA: DB: …
There is >>> it’s 
For some of them that use mount points, it looks like this since I separate them by HD size. But you can sort them out any way you want (just pretend “MMX” is “CHIA” or “HD” lol)>
Ever find out what those
Are
It means, “Warning Warning - how dare u spend so much on HDs” 
says wife 
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Well we could get just 8 100TB SSD to fit into an 8-bay and we would be set.
haha, say to her that your 401k for next 20 years
If you use mount points there is no limit to the number of drives you may have on one system, provided that your disk controllers have more capacity. I have a SAS controller that can support 2048 SAS devices. This includes expanders and disks. So for instance if I had a system with multiple PCIe expansion slots and the means to power and physically install thousands of drives then the sky is the limit really.
When you run out of letters for assigning it to your disks, you can create a Folder and mount the HDD’s in there and name them/number them as you want (it’s not clear if there is a limit, there should be a detailed technical explanation).
(That’s what I have done, here the link of the steps in Spanish I followed)
CĂłmo montar una unidad de disco duro como carpeta en Windows 10 (profesionalreview.com)
You can Google it in English: “How to mount a hard drive as a folder in Windows 10/11”
Saludos
Usually it is said that USB can manage up to 128 USB devices, but this is simply wrong.
Since it is not devices but USB endpoints. and there would be theoretically possible over 7k per USB root but in the end, usually only 128 / 96 or even only 64 endpoints are supported per Root USB Hub depending on the implementation of the chipset.
And as already said endpoints are not equal to devices, a HDD for example needs at least 3 endpoints (IN, OUT, Control).
Another problem is that when using USB3 the endpoints are doubled (for usb2 & usb3), a HDD connected via USB3 occupies 6 endpoints.
Another complication is that many HDDs require hubs, each hub can be branched a maximum of 4 times and requires an endpoint (control, with USB3 2 x control).
A USB3 16 port HUB therefore consists of 5 HUBS which then alone consumes 10 endpoints.
also the branching depth is limited to 7 levels whereby already the root USB hub takes one away.
The only good thing is that normally on common mainboards several Root USB Hubs are installed and it is possible by clever distribution to the different Root USB HUBs a reasonable number of HDDs can be connected.
Bad it looks for example with a RAS Pi here there is only 1 root hub and accordingly “few” USB devices can be connected. (with a small modification would still be accessible via the USB C power connector a 2 USB Root HUB).
In the end, it depends on the hardware used how many HDDs are connected to the maximum and it can not be said in general 128 USB devices can be connected.
Normally WiFi, Bluetooth and other devices on the mainboard are also connected via USB, which you wouldn’t expect at first glance. Of course these also occupy USB endpoints.
have a nice day
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Nice summary.
Although, I would disagree with that statement. In both cases (whoever is stating that 128 limit, or what you wrote there mentioning just “devices”) that text is not really precise. Maybe to clarify it (based on your summary), it would be better to say that:
USB Root has an addressable space of 128 addresses. However, not all USB Roots support the whole addressable space (e.g., RPi - as you mentioned it). Also, each physical USB device (USB Hubs, HDs, cameras, mouse, …) takes 1+ address; therefore that 128 limit is just theoretical. Also, it may be that older OSes have more limited USB support, thus crippling capabilities of those USB Roots.
Basically, the milage will vary depending on the mobo, OS, devices used (e.g., those Seagate USB Hub drives are potentially the biggest offenders and some old mobos using early USB 3 chips with limited addressable space).
Saying that, i am not sure what USB Root means exactly. If that is a physical thing (a chip on a mobo), than that chip sits on a PCIe bus. What most likely implies that by adding more PCIe cards will multiply the number of USB Roots on the box, as each such card will provide their own USB Root to the OS (still, it will be irrelevant how many USB ports are on such card, so one that has just 1 port may be as good as one with many ports - just one USB chip sitting on the PCIe bus).
I don’t have much USB experience on the driver level, so I am mostly parroting what other people said.
Yes, a USB root is a hardware component (chip) which is installed on the mainboard or expansion card. this usually has a port (tier 1).
Normally here is also directly connected to another hub (tier 2), these are then the ports on the back panel of the mainboard. This exception is usually the USB C connection here the one port is used directly so that the full 20G are available.
As you can see, before you have even connected a device, 2 of the 7 maximum possible tiers are already used up. the USB adapter also takes up another tier, so there are only 4 tiers left for USB hubs.
These limitations and the fact that USB is not a particularly energy-efficient protocol do not play a role in normal everyday life, because here the uncomplicated universal handling is in the foreground. But in terms of Chia and the fact that it can handle a lot of HDDs (over 100), USB is a bad choice because of all its limitations.
On a small scale, it is a simple solution for a smaller chia farm if you keep a few things in mind and it runs very stable.
I myself use USB for 48 HDDs on a single system and it runs absolutely stable and smooth.
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