SELFHOST.COMPUTER

Backup Size Planner

Deduplicated backups (restic, borg, kopia) only store what changed, so the repository is far smaller than "data size times number of snapshots". Enter your numbers to see how big the backup target needs to be, plus the retention command and cron line to go with it.

Not sure about the change rate? 0.2 to 1% is typical for app data and config. Databases dumped in full every day and busy file shares can be 2 to 5% or more.

How the estimate works

  • The first snapshot stores all your data once.
  • Each further snapshot you keep adds only what changed since the previous kept one. Overlapping changes count once, so a week of changes isn't seven times a day's.
  • Compression shrinks the total. Photos, video and archives barely compress, so choose "none" for those.

It's an estimate, not a guarantee. Large files that change completely each day (database dumps, VM images) back up worse than the model assumes, so give those a higher change rate.

Where should the backups go?

Not onto the same server. A second small VPS at a different provider or an S3-style bucket both work, and the restic guide shows the SFTP route. Provider choices are in netcup vs Hetzner vs Contabo, and tool choices in restic vs borg vs kopia.