This might be a basic thing, but I seem to be missing something.
I am using a RPi4. I am working with a thumb drive for the system and a USB-SSD for the user data (nextcloud). This all works well. My plan is to backup the whole thing via the built-in backup solution on an additional USB SSD. I can make a backup to the attached SSD without any problems.
But as soon as I plug the additional drive in, things get messy. The system seems to re-mount all devices with sda becoming sdc and so forth. This leaves me without the possibility to render a backup to the additional drive since all mounts get lost. I even have to unplug everything, reboot and re-mount the original two drives to get the system running again.
can you check dmegs for “under-voltage” messages? Sounds like it becomes power issues when you plug the stick in. Have you other disks attached? If yes, with dedicated power supply?
Yes, how do you power your external HDD/SSD? Especially on RPi4 it is important to use external PSU because USB ports of RPi4 are not designed to power larger devices.
Thanks!
Attached devices are a USB thumb drive and a USB NVME enclosure. No dedicated power supply. This setup is running well. A third drive causes the problems I described.