ZFS Backups
What this is about
When you open the Backups tab for your server, you'll see a banner telling you whether the node your server lives on uses ZFS for backups. This article explains what that means, why it matters, and what SuHosting is doing about it.
What is ZFS?
ZFS is a modern filesystem designed around scalability and resiliency — end-to-end checksumming to detect and repair silent data corruption, and a copy-on-write design that keeps data consistent even through crashes and power loss.
One of the features of the copy-on-write design enables is snapshots, and that's the part most relevant to backups. A snapshot is a read-only, point-in-time image of the entire filesystem. Because ZFS never overwrites data in place, a snapshot is atomic and instantaneous: it records the exact state of every file at a single moment, no matter how many files there are or how large they are.
Taking a snapshot doesn't copy anything up front and doesn't pause your server. The snapshot simply "pins" the blocks that make up the current state, and only changes made after the snapshot consume additional space.
Why ZFS backups are better
- Consistent backups, even while running. A ZFS snapshot captures every file at the same instant. Your world save, configuration, mods and databases are all frozen together as one coherent set.
- No downtime. Snapshots are taken in milliseconds. Your server keeps running and players stay connected while a backup is created.
- Fast and space-efficient. Because only changed blocks are stored, backups are quick to create and don't duplicate data that hasn't changed.
- Data integrity. ZFS checksums every block and can detect (and on redundant pools, repair) silent corruption, so a backup is far less likely to quietly rot over time.
- Quick restores. Rolling back to a previous snapshot is a near-instant operation rather than a slow file-by-file copy.
Why it matters that ZFS is not enabled on this node
If your server is on a node without ZFS, backups are created by copying files off the disk while the server may still be running. Files can change during the copy, which means a backup can capture an inconsistent or half-written state.
For many game servers this is a minor risk, but for games that store the world in a live database (Vintage Story is one — see the related article on backing up Vintage Story safely) a backup that overlaps a save can fail to load or lose recent progress.
On a non-ZFS node the safe approach is to stop the server before creating a backup. On a ZFS node that step isn't necessary, because the snapshot is already a single consistent point in time.
What SuHosting is doing about it
We're actively and progressively migrating all of our nodes to ZFS. This is being rolled out node by node so that every server eventually benefits from fast, consistent, zero-downtime backups by default.
If your server is currently on a non-ZFS node:
- No action is required from you — your server will be moved as part of the ongoing migration.
- In the meantime, stop your server before taking a backup if the data matters (especially for Vintage Story).
- If you'd like your server prioritised for migration, reach out to SuHosting support and we'll help where we can.
Once your server is on a ZFS-enabled node, the Backups tab will show a green banner and you can back up safely at any time.