The external HDD wasn’t working well, so I bought a NAS earlier. I chose it because it was a little higher than the introductory machine. I also wanted to use RAID 6 level ones. The reason is that I wanted to keep the level that is okay even if two drives die. It was my first time to buy a NAS, and I chose it because SHR seems to be interesting.
When I actually use it, it also functions as an application server, and it seems that various applications such as GitLab and Redmine can be installed, so I think it was better than the high end.
Since the load increases when using the WebUI, I think that the backup for the main purpose is not so heavy. For backup, a backup application is also distributed, but in the end, I settled on rsync via smb.