Restic or Borg: which is better for offsite backups to your own server?

What does the server need for restic, and for Borg?

restic needs nothing of its own on the server. Its documentation asks for an SSH server that knows your public key, since a password prompt would stop automatic backups. For an append-only target, run restic's rest-server instead; it listens on port 8000 by default.

Borg's quickstart says remote repositories are fastest and easiest when Borg is installed on the remote host. The client then talks to borg serve over SSH. Without Borg on the server, you can mount the remote filesystem, but the docs warn that not every filesystem is stable enough for backups.

restic turns any SSH account into a backup target; Borg asks for one server package and gives a tighter forced command.

# restic over SFTP: only SSH and a key on the server
restic -r sftp:[email protected]:/tank/restic init

# Borg over SSH: Borg 1.4.5 installed on both sides
borg init --encryption=repokey-blake2 ssh://[email protected]/tank/borg

# On the server, ~backup/.ssh/authorized_keys pins the key to one repository:
command="borg serve --append-only --restrict-to-path /tank/borg",restrict ssh-ed25519 AAAA... client@laptop

How do restic and Borg encrypt, and who holds the key?

Both encrypt on the client, so the server stores only ciphertext. They differ in how much choice they give you.

• restic encrypts everything in the repository with AES-256 in counter mode and authenticates it with Poly1305-AES. Your password unlocks the key through scrypt. Even the local cache is encrypted.
• Borg sets the mode at borg init. repokey keeps the encrypted key in the repository; keyfile keeps it on the client. Borg's docs say to export the key with borg key export and store it away from the backed-up system.
• Kopia has no unencrypted mode. It encrypts contents and file names with AES-256 or ChaCha20.

The wider picture is on client-side encryption for backups.

Which one keeps old backups safe if the client is hacked?

Both, if you set it up. rest-server's --append-only mode allows new backups but prevents deletion and modification of existing ones. Borg's append-only mode refuses to overwrite or delete committed data.

Borg documents the catch. Prune and delete still run in append-only mode; they only mark data as deleted. The next write in normal mode, such as a prune from your admin machine, removes that data for good. So run borg check before any pruning, and keep a hard-link copy if you suspect an attack. Recipes for both tools are on making backups immutable on your own server.

Is Borg 2 ready, and what happens to Borg 1 repositories?

Not for production yet. Borg 2.0 is in beta: 2.0.0b25 came out on 27 September 2026, and the 1.4 series remains the release marked Latest. Borg 2 uses a new repository format. borg transfer --from-borg1 copies archives from a Borg 1.x repository into a new Borg 2 one. Borg 2 must then run on both client and server.

Start new offsite repositories on Borg 1.4.5 today, and plan the move to Borg 2 as a transfer, not an upgrade in place.

Where does Kopia fit?

Kopia is the third option, and the one with an official graphical interface. Version 0.23.1, released on 16 June 2026, fixes a rare race condition that could lead to data loss, and the maintainers recommend upgrading. It writes to SFTP, S3-compatible storage and several clouds, or to a Kopia Repository Server you run yourself. Its ransomware guide relies on S3 Object Lock in compliance mode, or on access keys without delete rights. Pick Kopia when the people running backups want a window, not a shell.

How big a server do restic or Borg need?

Size the pool for one full copy of your data, plus the changed blocks of every version you keep. Deduplication and compression shrink both; how much depends on your data. Then add parity: ten 10 TB drives in RAIDZ2 leave 80 TB for the repository.

On 2 November 2026, no-KYC hosts taking crypto charged a median $6.70 per TB a month from 36 TB. From 72 TB, the median fell to $4.86. Hold 40 costs $5.02/TB and Hold 100 $3.77/TB, raw. Every term is on the hold price list. For whole virtual machines, an offsite Proxmox Backup Server is the closer fit.