the conpany i work for is making a proyect, we made Modbus RTU connection using raspberry pi 3 as a gateway, and saving the data to Mysql. this proyect have to be 24/7 and running forever, im wondering what will be the best SD? or should i use USB? or a HDD? also, about the power supply, what could be the best for this proyect?
Consider using externally powered SSD or spinning disks (depending on how much data storage is required). Have a look at external 5.25” drives in enclosures with good reviews. I would personally use a Synology Diskstation, which will you upload backups to a RAID1 mirror on your LAN.
You should script a full backup (with for example
rsync -au /path1/source /path2/destination) to run daily, at 1AM, or whenever load is expected to be minimal.
If using flash memory locally on the Pi, leave 10-20% of space unallocated for TRIM. Gparted will be useful for you to do this.