How many drives on a single USB port?

[mkvfanclub]

Hi,

So I want to speed up my DVD rips. I have thousands of DVDs so it makes sense to run multiple copies at the same time and rip multiple DVDs at once using multiple USB drives.

So what I'd like to know is how much of a single USB 2.0 port does MakeMKV use when a USB 2.0 DVD drive is connected to it?

Example, can I connect 3 USB drives to a single USB 2.0 port, run MakeMKV on all 3 and get full performance from all 3? Or will the USB bandwidth be full by just a single drive or two drives? Or can I run 6 USB drives on a single USB 2.0 port and all will run at maximum performance with MakeMKV on each?

Also, if I connect my USB 2.0 drives to a single USB 3.0 port, does that give me more bandwidth available (given the drives will be running in USB 2.0 mode but presumably there is plenty of spare capacity with USB 3.0 or doesn't it work like that?) How many USB 2.0 drives could I connect to a single USB 3.0 port with MakeMKV running on all of them before I would fill up the USB bandwidth?

I'm just trying to connect as many USB 2.0 drives as possible to a single USB 2.0 or USB 3.0 port without saturating USB bandwidth and losing performance.

Thank you.

[Woodstock]

That depends on your operating system and hardware.

There is a limit to how many USB devices can be attached to a USB controller. Any hubs on the controller count as a device, too.

A port has limited power, and USB drives have a tendency to absorb as much as a port can (usually) give. And that power is divided between devices in a non-powered hub.

But bandwidth of the USB will be problematic - a USB2 device only goes USB2 speeds, even when plugged into a USB3 port, so your USB3 port cannot talk at USB3 speeds when USB2 devices are attached and active. I have played with 2 USB2 drives on the same USB controller, and that works (optical read speeds leave big enough gaps to interleave at least 2 drives worth of data). But I have also seen significant slowdowns when the network controller is also a USB device.

As far as MakeMKV is concerned, though, it's up against operating system limits for block devices if you "go wild" with lots of hardware.

Since I like to preset the file names when I start a rip, I found the practical limitation on my time was 5 drives, because the first would generally finish ripping before I could finish setting up the 6th disk for ripping. These weren't USB drives when I tested this, but SATA drives split between multiple computers.

Your connection to the storage device can also limit what you can do.

[Username1267]

If you use a magnetic hard drive then don't forget that the read/write head will start to move around reducing the writing speed dramatically. When I copy a big file from A to B then my hard drive is so bussy that it isn't even fast enough anymore to store the data comming from 1 DVD drive (about 12 MB/s).

[mkvfanclub]

Ok I'm using only SATA/3 SSDs (no mechanical hard drives in my computer) and it's Windows 7 64-bit.

Intel i7/6700
16GB memory
Nvidia RTX 2080
2 x Samsung 8TB SSD (QLC)

and the DVD drives are LG USB2.0 GP57 range

and I'm only ripping DVDs (not Blu-Ray).

[mkvfanclub]

Just to follow this up.

What I ended up going with is a front panel 4-port USB2.0/USB3.0 drive bay. It contains 2 x USB2.0 which I connected to the USB2.0 header on my motherboard and 2 x USB3.0 which I connected to another USB2.0 header on my motherboard using a USB3.0 to USB2.0 converter cable. This gives me 4 x USB2.0 ports on the front panel. I have a DVD drive connected to each one and all 4 work perfectly.

I also have 2 x USB3.0 ports built into the computer case which I could use for 2 more DVD drives if I wanted. These ports connect to a USB3.0 header on the motherboard.

My conclusion (with some trial and error) is that it's fine to connect one DVD drive per USB port on the computer as long as no more than 2 of these ports are connected to a single header on the motherboard.

It's best not to use USB hubs as they can easily cause damage to the USB headers on the motherboard. I initially did try to connect 4 DVD drives to a 4-port USB3.0 hub but doing so overloaded the motherboard USB header that the hub was connected to and the motherboard USB header is now damaged as a result. I have a spare motherboard USB header that I'm using so it's fine but this experience put me off using USB hubs.

I did ask USB PCI card manufacturers about PCI card options but, even with the 4 port+ cards, the manufacturers don't recommend more than a couple of DVD drives connected at the same time because of the possibility of overload. So I didn't go down this route.

This is the USB drive bay I am using now:
https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1

And this is the USB3.0 to USB2.0 converter cable:
https://www.amazon.co.uk/gp/product/B07 ... UTF8&psc=1