Is the R610 Is Good for Proxmox Backup Server? I know it’s older but will it be a good production server? If so, how would you dress it up? If not, why not?
Depends on the CPU. If it's an Intel Xeon 56xx CPU you'll have hardware AES, so the TLS transport encryption will be "fast".
With a 55xx Xeon it'll definitely slower because of lacking hardware AES.