A. Dumas wrote:
> Roby  wrote:
>> Or is it better to replace the SD as soon as I go to the remote
>> location?
>
> Definitely. Because you can't get to it so often for maintenance, I suggest
> using a hard disk (maybe ssd, but hdd works fine for me) instead of an sd
> card. See
>
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/msd.md

Dennis Lee Bieber wrote:
> ----cut
>  It is a PARTITION on an MMC block I/O device. (Mine shows partitions 1,
> 2, 5, 6, and 7)
>
> pi@raspberrypi:~$ ls -l /dev/mmc*
> brw-rw---- 1 root disk 179, 0 Sep 24 18:53 /dev/mmcblk0
> brw-rw---- 1 root disk 179, 1 Sep 24 18:53 /dev/mmcblk0p1
> brw-rw---- 1 root disk 179, 2 Sep 24 18:53 /dev/mmcblk0p2
> brw-rw---- 1 root disk 179, 5 Sep 24 18:53 /dev/mmcblk0p5
> brw-rw---- 1 root disk 179, 6 Sep 24 18:53 /dev/mmcblk0p6
> brw-rw---- 1 root disk 179, 7 Sep 24 18:53 /dev/mmcblk0p7
> pi@raspberrypi:~$
>
> and partition 7 is the root file system
>
> pi@raspberrypi:~$ cat /etc/fstab
> proc            /proc           proc    defaults          0       0
> /dev/mmcblk0p6  /boot           vfat    defaults          0       2
> /dev/mmcblk0p7  /               ext4    defaults,noatime  0       1
>
----- cut

Thanks to @A. Dumasper for the suggestion of HD or SSD ....
Thanks also to @Dennis Lee Bieber for the important details ...

I use one of the USB ports (rpi3 B) to manage and control the APC UPS,
but I don't think that putting an HD / SSD USB on one of the free ports
can cause problems ....
I could try, or I could wait for the RPI4, hoping it has a dedicated
port for external HD or a faster USB 3.1 port.
..... I'll see what to do ...Thanks

--
Roby

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