# SATA2USB/Docking station suggestion

## axl

Hello

I am looking for a decent way to connect Raspberry PI 4 to 2 sata (mechanical) drives (10Tb WD reds if it makes any difference). What I am looking for is something that would work 24/7; something that would be compatible with linux; something that would be self-powered (not drain the PI's usb); and finally something that would get as close as possible in performance to the network saturation point.

In a normal system, these drives have no problem reaching that 100 MB mark. I tested the PI with a ssd device, and simple usb2sata adapter and it's almost getting there. 90/100. It's not perfect but it's good enough for me. These 2 drives also are in raid1. I expect that would impact the performance, at least while writing stuff on the disks. I am prepared to take that hit as well.

The adapter I have now is powered just by USB, thus cannot be used for mechanical drives because it lacks 12v power source. I was thinking something like this:

https://www.gmb.nl/item.aspx?id=8473

Or maybe this:

https://www.axagon.eu/en/produkty/adsa-st

There are tons of brands of these things that I never heard about. They all seem to be identical in many ways and it's almost impossible to find 2 reviews that agree with each other. Any recommendation based on actual experience with these things would be appreciated.

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## axl

https://www.eteknix.com/wp-content/uploads/2017/12/WD-RED-10TB-Photo-top.jpg

Btw, based on this picture, you can see in the top left corner there is a line starting with "RATED" which details the power consumption at 5v and 12v. I am assuming the 12v is required for the motor and electromagnet that moves the heads, and the 5v for the logical electronic stuff. 

But all the docking stations I looked at, detail their power adapter as being 12v. Which leads me to believe that even when these things are powered, they just power the 12v part of the hdd, but still drain 5v from usb. The first one (gembird) power connector seems to be more than 2 pins, so maybe that one powers both 12v and 5v. Not sure. The specifications only mention 12v. 

I'm not too worried about these 2 drive, because 400mAh * 2 = 800mAh < 1.2 Ah that the pi can offer. As long as the docking station(s) itself doesn't use more than 400mAh, I should be ok. 

https://www.forit.ro/images/products/img1/58494/full/wd-hard-disk-red-4tb-sata-iii-intellipower-64mb-26710.jpeg

But I also have 2 of these. And these as you can see use 600mAh. x2 = 1.2 Ah and that's it. No more power for the docking station (s)... kinda worrying. So that's why I'm looking for a solution that powers _both_ circuits. 

If I can help it, I would like to avoid a 5v power supply just for this. I mean the pi's have their own adapters, the drives should also be powered just by the docking station without any more complications. But I'm not sure these things convert internally the 12v to 5v for the logical circuit.

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## NeddySeagoon

axl,

These dodas with a 12v supply only often contain a DC to DC converter to derive the 5v from the 12v supply.

Others as you say will obtain the 5v from the USB bus.

There is usually no way to tell is advance.

Soft raid over USB ... shudder. Good luck with that.

I would look at something with a network connection if I wanted raid on a Pi, or at least, something that didn't need kernel raid runnnig on the Pi.

That's probably a real NAS box which I'll guess is more that you want to spend.

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## pa4wdh

I'm using a Sharkoon Drivelink combo USB3.0 (https://en.sharkoon.com/product/1686/13760), and so far it has been working flawlessly with linux. I use it with a Seagate Barracuda 4TB mechanical drive and (among others) a Pi 2B for backups, and because it has it's own power adapter the Pi has no problem using it. I've even connected a PATA DVD drive to it and it works  :Very Happy: 

I don't know how it will work when used 24/7, the longest uptime with my usage is about 12 hours.

I agree with Neddy that RAID over USB is a Bad Idea: https://raid.wiki.kernel.org/index.php/Choosing_your_hardware,_and_what_is_a_device%3F#USB_devices

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## axl

Neddy: Yeah. A little more then I want to spend. I could just leave them inside my computer if I wanted that performance. I am looking for something light. They are never used at those speeds. 2-3 family members which use them over internet (which in my case is 100Mbps), and 2 kodi's in my house. That's about all they have to support. Even the idea of gigabyte only comes into play when I will write new stuff on them, which doesn't happen all that often. Performance is a secondary concern, if not tertiary. 

What does concern me is stability. And low power consumption. And well, removing them from my computer. Both to lower temperature in my case and ease the load, and to be able to shut down my computer when I don't use it without cutting access to these.Last edited by axl on Tue Apr 07, 2020 3:32 pm; edited 1 time in total

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## axl

pa4wdh: If raid will not want to play nice over usb, I could revert back to a rsync script to keep them in sync. No big deal if I have to abandon raid. As long as I can backup one over the other once a week, I'll be fine. Keep em coming. And thanks.

EDIT: also ... are these usb devices? are these sata devices? I'm not sure. "They have a timeout/disconnect mechanism which interacts very badly with the raid code". Do these devices have the limitations of memory sticks? Something tells me that refers to memory sticks, not these adapters. Bleah. I hate buying things just to test. The lack of specifications is just super annoying.

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## NeddySeagoon

axl,

One drive will be fine on USB.  I have a SATA SSD connected to my Pi via USB3 and its stable.

The HDD may go into a power save mode if you let it. Then you need to wait the spin up time.

USB is used to that, so not a problem.

Raid is not a backup.  

I have a USB to SATA doda that only needs the 12v supply for 3 1/2" drives.

That does not mean it always pulls 5v from the USB bus, just that it can.

It might even back feed the USB host with 5v when the 12v supply is provided.

These things can do horrible things like that.  I've never tested.

I could, because I have a USB cable that has the power wires cut. Don't ask :)

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## axl

Neddy, I was thinking of cutting those power cables inside the usb cable too. Just to be sure. Plus I have a few of these things:

https://www.robofun.ro/incarcator/voltmetru-si-ampermetru-charger-doctor.html

As for hdd sleep I am not worried. These red drives don't sleep and don't spin down.

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## axl

Neddy as far as raid/backup goes, these are not important or vital data. It's just copies of my own cartoons and tv shows and movies I copied over from my dvd's or bluerays. If I loose them, It's no big deal. The second drive is there just in case the first one breaks, and that is enough for this application. Not exposed over the internet; have to vpn inside the network to see it. I am not worried about security or anything like that.

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## NeddySeagoon

axl,

In USB3 cutting both power wires is fine as the data signals are differential.

With USB2 and USB1, its one wire each way with the 0v. Cutting the 5v is good. Cutting the 0v will reduce the noise margin on the data link, so you may want to leave the 0v intact.

Those USB meters look handy.

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## axl

 *NeddySeagoon wrote:*   

> axl,
> 
> In USB3 cutting both power wires is fine as the data signals are differential.
> 
> With USB2 and USB1, its one wire each way with the 0v. Cutting the 5v is good. Cutting the 0v will reduce the noise margin on the data link, so you may want to leave the 0v intact.
> ...

 

You mean cut only the positive and leave the ground? If so, it would make a bit more sense to make a cord with a switch for testing. 5v on, 5v off. A simple toggle. 

 *Quote:*   

> Those USB meters look handy.

 

They sure are.

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## NeddySeagoon

axl,

Yes. Leave the ground.

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## axl

So my first 2 docking stations arrived. I went with the german firm gembird (it's still made in china... but according to german plans). I posted specs before. I said I was going to pick this one because based on the connector, I thought the 5 pins connector will use an external power transformer for the 5V. And I was right. 

It's german. It's hefty. And I'm filled with hope. 

This is the package. https://i.postimg.cc/zGwQ6DDB/package.jpg

this is the transformer. no internal unsafe duda (as neddy called it). 

https://i.postimg.cc/Pf4zgLY0/transformer.jpg

I will not be installing it today. But I expect in 2-3 days, it will be up. Anyway... very happy with my choice so far. 

Btw, I'm now using a rpi 3a as my router for a 100MBps connection... and it's doing fine (2 weeks in). This would be piece 2, into transitioning to a pi network. My goal is, again, being able to shut down the big computer.

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## axl

Let me ask another question. When I started doing this... it sounded stupid even to me. But as things progressed, I'm more proud and happy with my choices as I go along. 

I'm at a cross road.

I could go with individual power transformer for each pi, OR i could go with pi hats and a PoE switch. I was thinking a pair of this one: 

https://www.dlink.com/en/products/dgs-1100-08p-8-port-gigabit-poe-smart-managed-switch

Now I know... the switch breaks... you dead in teh water. That's why I said "a pair". I will only be using 6 pi's. maybe 7. The 8th port is for daisy chaining. And they are not that expensive for what they are doing. The pi hats on the other hand are very expensive compared to a simple transformer. Bull less cables. Plus... I have to admit, the only reason I am thinking about this is because it's cool. IT IS COOL.

What do you guys think?

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## NeddySeagoon

axl,

I have two PoE switches, both from Amazon warehouse, at very good prices.

Read the fine print on the PSUs many PoE switches are provided with inadequate PSUs.

The one in your link is only 64 W.  Say 15W per Pi ... that's only 4 Pis on PoE.

This is how vendors keep the cost down.

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## axl

Hmmm. Not worth it then. 64W is not a lot of watts. I thought... well, maybe I should have remembered my physics class from high-school. I thought the high voltage will somehow help, but Watts are watts. Thanks Neddy.

Will be reporting back once I finish my setup with the harddrives.

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## axl

btw, regarding this project, I got one of these:

https://www.tp-link.com/no/home-networking/smart-plug/hs110/

I don't regret buying it. I regret not having more money to buy a few more. But next month. 

https://www.evilbox.ro/linux/tp-link-hs110-smartplug-linux-monitoring-with-grafana/

my project is coming along nicely.

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## axl

Those gembird adaptors are quite cool. 2A for 12v, 2A for 5V. I used my dooda to measure the pi power output, and other than the tester, the gembird thing didn't draw any power from usb. which was exactly what i was looking for. this is a success story. I found what I was looking for. 

Second... that whole thing... you can't have raid on usb... doesn't apply to sata2usb adapters. well not anymore than a pc. 

And I posted about the smartplug. I just love that thing. I got three more. 

I am doing a smart house. 

I find this statement to be ridiculous. But I am doing it. And I felt the need to admit that to myself. I am doing the smart house thing. with ... well... many pi's. but those smart plugs are not bad either. 

depending on what you want from a smart plug. I wanted 2 things. to be able to shut it down remotely, and the ability to read the stats on usage with smth like snmp or smth. it has that. 

there are those: digital counter plugs. have to bend over, look at the screen where the plug is. this one has wifi. and judge me if you will, I kinda like it, got 1, then 3 more, and now I want 5 more. cron...

also there are titan gray/grey?! samsung memories. which are dirt cheap. like 10 bucks for me in romania. which are 200+MB/s. for a pi. 

I have been using tftp for boot and nfs for everything else. but 10 bucks for a medium made by samsung which promises to be 200MB/s... twice the network speed... Ima gonna take 6. for me, everything is 6. 6 pi servers to rule them all.  :Very Happy: 

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