- FreeBSD is the preferred OS for backup servers due to its ability to partition services via jails and VMs, and ZFS provides flexibility and data integrity.
- Backup servers should be hardened, encrypted (using GELI or ZFS native encryption), and ideally accessible only via VPN or LAN.
- Two main backup strategies: zfs-autobackup for ZFS-based systems (pull-type) and BorgBackup for non-ZFS systems (push-type), with per-server jails for isolation.
- Proxmox Backup Server can be run in a VM with data stored on a Minio jail, leveraging S3-compatible storage on the host ZFS pool.
- Local snapshots on the backup server (using ZFS) provide protection against ransomware or malicious deletion of backups.
- It is crucial to maintain both an external (different datacenter) and an internal (local) backup copy, with independent backups to avoid propagation of issues.
- Disk redundancy (mirror, RaidZ) is recommended for backup servers, as backups are as important as production data.