WD Red: External power supply problems

Dear community,

I’ve purchased two of the latest WD Red 2TB drives (WD20EFAX) on Amazon for my personal cloud at home. I’m running Ubuntu Server 20.04 LTS on my Raspberry Pi 4 4GB. I’m using SATA to USB adapters with power supply to power the HDDs and establish the connection with the Pi. I’ve tried two different brands for such cables: Inateck and Benfei.

The problem: If only one single drive is connected everything seems fine. It spinns and is mounted properly for multiple consecutive days in a row. Until I connect the second drive (The order is not relevant, both drives have that problem): One of them frequently stops spinning and boots up again a second after. The affected drive is therefore not mounted to the filesystem anymore. I suspect that both drives still drain power from the Pi’s USB ports rather than the SATA power supply adapters. The Pi is probably unable to power both drives simultaneously which results in one of them losing power.

I’ve contacted the WD Live Chat support. The friendly person I talked to said that WD Red drives support being powered by such adapters. He/She adviced me to replacing both drives. I highly doubt that both drives are defect, as both are brand new (so are the adapters). It seems very unlikely to me. I’m having this problem for a while now and it really gives me headaches. That’s why I decided to start a new discussion topic in this forum. If there’s anyone who can tell me whether WD Red NAS drives support this setup or can suggest a solution to this problem I would be very grateful!

The Raspberry Pi is not designed for desktop hard disks. The Pi is fine with a micro SD card. So put the hard disks into a desktop machine.

If storage is an issue get a larger micro SD card which are now in the 1TB range.

Why is the Raspberry Pi not able to deal with those drives, can you be more specific? I don’t see how a RPi is in this context any different from a Desktop PC. It’s not uncommon to set up a NAS or cloud on the Raspberry Pi with multiple externally powered drives connected. I see many people doing that on the internet but I can’t find any new insight into my problem or what is causing it.

1TB SSD would probably not be enough (I already hoard 800GB of photos). In addition to that are reliability and availability very important to me. That’s why I want two drives connected via RAID or rsync. I want my drive to be available 24/7 with as little power consumption as possible. That’s why I’ve purchased those Red drive, as I’ve heard that they are built just for that. I’ve tested the drives on my laptop too and I’m having the same problems there. WD didn’t mention anything (on the Amazon page) on which hardware is supported and which is not.

The connect the Pi to a LAN and copy images etc to a desktop with the hard disks. The Pi is also not the best option for a NAS ether as it has no PCIe slots etc

I’m sorry but I can’t quit understand your answer. My question was why WD Red drives are not compatible with the Raspberry Pi (if they actually are not). There was no hint or information on the Amazon page regarding supported and unsupported hardware. As the Raspberry Pi is a normal ARM 64Bit and Ubuntu-Server a widely used operating system, I was not able to predict such complications. As I’m having the problem with my Laptop too (x86 Ubuntu) I can’t believe that the Raspberry Pi is the root cause of the issue. If the Raspberry Pi is the problem nonetheless, can you please be more specific on why that is? As of now I see no other solution than replacing or returning the drives as defect.

The Pi is a small board computer and does not have nearly enough power.

If you need hard disks on the LAN go get a low end NAS box

I know that. The Pi is not able to power both drives by himself. That is precisely why I’m using external power supplies. In general, the drives are working with the Raspberry Pi. It’s just the power supply that is not: The drives are not powered by the power supplies but by the USB ports (Which they are obviously not supposed to). The drives should be able to support this setup, as nothing else was mentioned on the Amazon page (or WD Website). The Raspberry Pi is not a microcontroller or something like that. It’s a small personal computer. Please don’t answer if you don’t know a profound answer to my question.

You can test this hypothesis by connecting a powered USB 3 hub between the PI and the second disk. Then any power via de USB-connection will be drawn from the USB-hub.

Thanks! Good idea. I will test it and keep you posted.

USB 3 should be able to deliver 900 mA on each port, for two ports that will be 1800 mA together. The PI has a self recovering fuse that allows for 2000 mA to be drawn in total by all USB-ports. The load will be 90% and it should work. But it is possible that one or both of the USB to SATA bridges have a slightly higher initial current draw. And might therefore trip the 2 A poly fuse in the PI.

This documentation suggests that the Pi can deliver up to 1200 mA in total. I can derive from the WD RED product brief that the drives in read/write require 4.1 W / 5.1 V ≈ 800 mA. I’m assuming that there are 5.1 V on the USB ports, but I could be completely wrong here. I’m not very much into electrical engineering, please correct me if I’m wrong.

But either way these specifications make it even worse for two drives being connected simultaneously. I will definitely test a USB3 hub as soon as I can get my hands on one.

Ah ok, there seem to be multiple poly fuses on the PI and the 2 A one I was talking about might be on the main input. I got those mixed up.