josephchrzempiec
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How many 2.5" drives?

Wed Jun 05, 2019 7:17 pm

hello i was wondering how many 2.5" drives can the Raspberry pi power up without using any External power? Besides a Single Power supply powering the raspberry pi.


The power supply i have on the raspberry pi is a 5v 5 amp power supply. But I'm not sure how many drives can it handle? I'm working on building a NAS or SNAS system so i wasn't sure.



Joseph

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Re: How many 2.5" drives?

Wed Jun 05, 2019 7:29 pm

Regardless of how big your power supply is, ( 5A ) the pi can only supply a maximum current of 2.5A minus what ever current it is using its self, so realistically about 1-1.5A max for external devices like your drives.

So to workout how many drives you need to know what maximum current they draw then you will know how many you can power from the pi directly , I suspect 1 may be 2.
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HawaiianPi
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Re: How many 2.5" drives?

Wed Jun 05, 2019 7:52 pm

Which model of Raspberry Pi?

Assuming a B+, 2B or 3B(+), the polyfuse will only pass 2.6A, so any power supply stronger than that is wasted.

The 5V/2.5A power specification includes 1.3A for the SoC and 1.2A for the USB ports (total for all 4 ports, with no per-port limits). Any accessories, such as other USB devices or GPIO powered devices and HATs will reduce the power available to the USB ports.

That will almost certainly limit you to a single USB powered HDD. I did manage to spin up and mount a pair of WD hard drives, but I could only access one at a time. Any operation involving both (copy from one to the other) resulted in one or both drives disconnecting.

More than one power efficient SSD could work, but power requirements for SSD varies a lot, so it would depend on the drive models.
Last edited by HawaiianPi on Wed Jun 05, 2019 7:58 pm, edited 1 time in total.
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josephchrzempiec
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Re: How many 2.5" drives?

Wed Jun 05, 2019 7:58 pm

Hello I'm very sorry i forgot to put that in there. I have a raspberry pi 3B 4 port usb on there. I can manually wire up each drive with a lot a wires and make it clean. I was just trying not to solder in some wires in case later on i want to use the USB to sata adapters for something else. I also have 4 Western digital SSD i can use as well. They are only 250GB each one but still be enough for what I'm doing.



Joseph

LTolledo
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Re: How many 2.5" drives?

Wed Jun 05, 2019 10:12 pm

On my actual test, on the condition stated above

the answer is "one-HDD", or "two-SSD"
One-HDD + one SSD is a "hit or miss"

and will depend on the SATA to USB adapter cable.....

if you want more HDDs/ SSDs/thumbdrives (max is 6 drives, regardless of type) you need ton have those connected via a powered hub

you can test it yourself and share to us your results
that way you can inform others as well....
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Imperf3kt
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Re: How many 2.5" drives?

Wed Jun 05, 2019 10:30 pm

OP states they have a 5A power supply, so in theory they could power the Pi and split the power to the HDDs directly from the PSU, bypassing the Pi's ~2.6A limit.

That might afford them three drives, potentially four - assuming approximately 1A per HDD
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josephchrzempiec
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Re: How many 2.5" drives?

Wed Jun 05, 2019 10:34 pm

The only problem i have is that i have to manually solder wires to the usb to sata adapter or cut the usb wires and power like that. And still share a common ground.

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Imperf3kt
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Re: How many 2.5" drives?

Wed Jun 05, 2019 11:42 pm

You could cut the 5v trace running to the USB ports on the Pi itself. That way you could solder a single, sufficiently thick, wire in its place, plus a ground wire.

It's cumbersome, and voids your warranty, but probably your most compact option.
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Re: How many 2.5" drives?

Thu Jun 06, 2019 2:38 am

Perhaps its wise to consider using 2x psu's ...
fwiw my approach was to use a seperate pc psu to supply 5v needed for the usb hub and 12v needed for the 6x external HDDs i need rare and infrequent access to. this allowed me to turn power on/off to the disks via the pi on demand when the data on the disks is required (using a mqtt enabled smart switch).

and to stop back powering the pi from the usb hubs 5v supply i only needed to snip the +5v wire connecting the slave USB connector to the hub PCB.

Node Red issues the mqtt command to power on the disks waits 60 seconds and then triggers a shell script to mount the drives, when finished with the disks another flowette calls an unmount scrip before issuing the mqtt to power of the hub/hdd psu. Thanks to the alexa-local node i can issue the disks on/off commands verbally which still tickles me a bit ;)

josephchrzempiec
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Re: How many 2.5" drives?

Thu Jun 06, 2019 4:10 am

Hello all thank you for the information. This is what i have came up with is i found a 6" inch USB extension. and cut into it for the power then heat shrink it. https://www.ebay.com/itm/291083347600 i think this will be the best thing instead of cutting into the Pi or the wiring for the drives USB wires.


Joseph

josephchrzempiec
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Re: How many 2.5" drives?

Thu Jun 06, 2019 9:52 am

Just a update. I did order some of these. But i had a old USB extension that my cat chewed up a while back i shorted up and sense i only had one I can power one drive off of it and two drives by the raspberry pi so that makes three i can power up with no problem. that is good thank you all for the help. Now i just have to wait into the other ones come in to power the forth one up.

fanoush
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Re: How many 2.5" drives?

Thu Jun 06, 2019 1:58 pm

josephchrzempiec wrote:
Wed Jun 05, 2019 10:34 pm
The only problem i have is that i have to manually solder wires to the usb to sata adapter or cut the usb wires and power like that. And still share a common ground.
Western Digital sold their PiDrive hard drives with splitter cable. The power went from power supply first to HDD then to pi, see e.g. https://uk.pi-supply.com/products/wd-pidrive-cable

josephchrzempiec
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Re: How many 2.5" drives?

Thu Jun 06, 2019 2:12 pm

My usb to sata external adapter uses a male A to male A cable.

chwe
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Re: How many 2.5" drives?

Fri Jun 07, 2019 12:02 am

HawaiianPi wrote:
Wed Jun 05, 2019 7:52 pm
More than one power efficient SSD could work, but power requirements for SSD varies a lot, so it would depend on the drive models.
and the used USB-SATA adapter..
LTolledo wrote:
Wed Jun 05, 2019 10:12 pm
One-HDD + one SSD is a "hit or miss"
yeah.. let's add more cause more is better.. more data corruption due to things go worse over time on the other hand is.. not as funny. :P
josephchrzempiec wrote:
Wed Jun 05, 2019 10:34 pm
The only problem i have is that i have to manually solder wires to the usb to sata adapter or cut the usb wires and power like that. And still share a common ground.
likely that powering over GPIO header skips the 2.6A diode (didn't check the snippet of schematics which are open accessible), probably not recommended by the people here.. But often done on SBCs which have too much consumption for a badly chosen powering solution (e.g. microUSB). But no experience on the RPi.. Mine runs headless without anything except camera so I don't have powering issues at all.. All 'NAS boxes' are different SBCs with reliable powering for such an use-case.
PhatFil wrote:
Thu Jun 06, 2019 2:38 am
Perhaps its wise to consider using 2x psu's ...
fwiw my approach was to use a seperate pc psu to supply 5v needed for the usb hub and 12v needed for the 6x external HDDs i need rare and infrequent access to. this allowed me to turn power on/off to the disks via the pi on demand when the data on the disks is required (using a mqtt enabled smart switch).

and to stop back powering the pi from the usb hubs 5v supply i only needed to snip the +5v wire connecting the slave USB connector to the hub PCB.

Node Red issues the mqtt command to power on the disks waits 60 seconds and then triggers a shell script to mount the drives, when finished with the disks another flowette calls an unmount scrip before issuing the mqtt to power of the hub/hdd psu. Thanks to the alexa-local node i can issue the disks on/off commands verbally which still tickles me a bit ;)
:shock: :lol: sounds funny and insane at the same time..
josephchrzempiec wrote:
Thu Jun 06, 2019 9:52 am
Just a update. I did order some of these. But i had a old USB extension that my cat chewed up a while back i shorted up and sense i only had one I can power one drive off of it and two drives by the raspberry pi so that makes three i can power up with no problem. that is good thank you all for the help. Now i just have to wait into the other ones come in to power the forth one up.
I would suggest to test the setup for reliability (e.g. data corruption) before I would run such a setup 'productive'...

If for whatever reason it has to be a RPi I would opt for a 'power sombrero'.. There are a few out for the "RPi formfactor". One of them even provides two USB A receptacle for proper powering with y cable solutions..

At least two 'competitors' provide boards with 'SATA hats' (over PCIe) with a sane powering solution for up to 4 discs (12 and 5V) on ARM based SBCs.

josephchrzempiec
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Re: How many 2.5" drives?

Fri Jun 07, 2019 7:35 am

I have actually mange to get 4 out of the 4 drives working. I just need to get the cable for the forth one. And when it comes in i can do that.

PiGraham
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Re: How many 2.5" drives?

Fri Jun 07, 2019 7:51 am

You should try to test a maximum load condition. Four drives all spinning up at once and moving the heads at the same time could be very different to 3 drives idling and one active. Make sure you don't loose drives at moments of peak power demand.


Your best option for power distribution is probably to wire direct from the PSU to the 5V rail on the USB/SATA adaptors and disconnect the 5V wire from the USB cable

josephchrzempiec
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Re: How many 2.5" drives?

Fri Jun 07, 2019 8:30 am

Hello i have them in a Raid Config mirroring so it writes to them all at once. 3.8 amps so far with the raspberry pi. I'm not using any GPIO pins off the raspberry pi everything is powered through a 5v 5 amp Converter. I have a 12 to 24v in and 5v 5 amp out converter. The pi is powered through the raspberry pi. Micro usb. The Hard drives are powered directly to the Converter. I put a full load of files on it anywhere from 20 MB up to 1 GB files for test and the peek i got total is 3.8 amps. With the last drive I'm maybe looking at 4.2 to 4.5 amps maybe if any problem i do have a second Converter i can use. The power supply i have is a 12v 20 amps supply.

ejolson
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Re: How many 2.5" drives?

Fri Jun 07, 2019 6:46 pm

josephchrzempiec wrote:
Fri Jun 07, 2019 8:30 am
Hello i have them in a Raid Config mirroring so it writes to them all at once. 3.8 amps so far with the raspberry pi. I'm not using any GPIO pins off the raspberry pi everything is powered through a 5v 5 amp Converter. I have a 12 to 24v in and 5v 5 amp out converter. The pi is powered through the raspberry pi. Micro usb. The Hard drives are powered directly to the Converter. I put a full load of files on it anywhere from 20 MB up to 1 GB files for test and the peek i got total is 3.8 amps. With the last drive I'm maybe looking at 4.2 to 4.5 amps maybe if any problem i do have a second Converter i can use. The power supply i have is a 12v 20 amps supply.
This sounds like a well thought-out solution. Would it be possible to upload a photograph showing how you ran the wires?

josephchrzempiec
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Re: How many 2.5" drives?

Fri Jun 07, 2019 6:55 pm

I'm wiring up the other last drive today. I will upload photos when I'm done.



Joseph

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Re: How many 2.5" drives?

Fri Jun 07, 2019 7:32 pm

If possible I would check the start up current draw as well.

With the Pi using lots of processing and the drives fighting inertia I would think this is the worst case.

Corporate wise, the SAN units phased power on over the three drawers and the old AS/400 did it by rack - 6x19 inch cabinets as tall as me controlled by a flick switch that you could flick up with your little finger to power on :shock:
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