Jim Jackson wrote:
> On 2019-03-27, Roby  wrote:
>> A. Dumas wrote:
>>> I got a Seagate 1TB external 2.5" hdd for ?50, usb-powered by the 3B+ Pi
>>> without problem, that's with the RPi official 2.5A adapter. WD is fine,
>>> too, I'm sure (or some will say better). You can set "max_usb_current=1" in
>>> /boot/config.txt to double the available power via usb, but that wasn't
>>> necessary for me.
>>
>> Thanks @A.Dumas for the info
>> But from the site www.raspberrypi.org I read these RPI technical
>> specifications:
>> "The USB ports on a Raspberry Pi have a design loading of 100mA each -
>> sufficient to drive" low-power "devices such as mice and keyboards.
>> Devices such as WiFi adapters, USB hard drives, USB pen drives all
>> common much more current and "........." The maximum power the
>> Raspberry Pi can be used is 1 Amp. If you need to connect to the USB
>> device that will take the power requirements above 1 Amp, then you must
>> connect it to an externally-powered USB hub"
>
> I use several "WD - Elements SE Portable Hard Drive" and an older WD
> Pi-Drive. All have just a USB connection, and are powered by that USB
> connection. They work fine with a modern Raspberry Pi. I even have one
> working with an old Pi 1 B+.
>
> My only concern is that they are appear to be designed for occasional use,
> not for being on all the time. Even so, I use one in my always-on home
> server, a raspberry pi 3B with a WD USB drive. It's been working for
> nearly 18 months. My backup server is the Pi 1B+ with a large capacity WD
> USB drive.
>
> These disks are mostly sold for external backup or portable storage. The
> disks inside are 2.5" drives and take maximum, roughly, 0.5A of current,
> which is well below the 1A max for the Pi USB total current. I have not
> succeeded in using 2 such drives on a Pi - the Pi doesn't boot. The in
> rush current on start up is too much.
>
> I think you will find the general performance of the Pi will be a better
> with a USB connected hard drive or SSD. The speed of the SD card interface
> is not brilliant.
>
> good luck.
> Jim

Thank you very much for sharing your experience.
I found in the drawer an old 2.5" 30Gb Hitachi Model DK23EA-30 ATA100
disk (2MB buffer size) that I will put in a USB-ATA box.
Although the HD has low performance I think it should be fine .... so
even the USB2 port is not fast ...
When I go to the remote location I will try to mount it ....
Thanks Jim
Bob

--
Roby

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