BtrfsSnapshots

BtrfsSnapshots refer to the snapshot capability of the Btrfs filesystem, which creates point-in-time copies of subvolumes without duplicating data. Snapshots use the copy-on-write mechanism, so initial snapshots share data blocks with their source and only diverge when either side is modified. This makes snapshots lightweight and inexpensive to create and maintain compared with full copies.

Snapshots can be created as read-only or writable. A read-only snapshot cannot be modified, making it suitable for backups and archival use. A writable snapshot can be changed and will diverge from the source as writes occur. Common commands include btrfs subvolume snapshot -r SOURCE DEST for a read-only snapshot, and btrfs subvolume snapshot SOURCE DEST for a writable snapshot.

As subvolumes, snapshots exist within the same Btrfs filesystem and can be used with Btrfs send/receive to stream incremental changes to another location. This enables efficient backups, migrations, or replication of states. The incremental send feature relies on existing snapshots to minimize the amount of data transferred.

Management considerations include space usage and lifecycle. Snapshots consume space as the system writes new data to either the source or the snapshot, so a large number of snapshots or heavily changed data can grow storage usage. Deleting unneeded snapshots reclaims space. While useful for testing, upgrades, rollback, and quick restores, snapshots are not a substitute for offsite backups or disaster recovery plans, and they rely on the health of the underlying storage.

Limitations and best practices: organize subvolumes to enable meaningful snapshots, use read-only snapshots for backups when possible, and periodically prune old snapshots to control space. Integrate snapshots with a broader backup strategy for robust data protection.