Starting with v1.6.0, Longhorn allows you to configure the maximum snapshot count and the maximum aggregate snapshot size for each volume. Both settings do not take into account removed snapshots, backing images, and volume head snapshots. When either of these limits is reached, you must delete snapshots before creating new ones.

In earlier versions, the maximum snapshot count is not configurable (the value is 250) and there is no way to limit snapshot space usage.

Settings

Global Settings

snapshot-max-count: Maximum number of snapshots that you can create for each volume.

You must specify a value between “2” and “250”. Longhorn requires at least two snapshots to function properly, particularly during volume rebuilding. One snapshot is created when the existing snapshots are merged, while the other snapshot is created during the rebuilding process. The default value is “250”.

When you create a volume without changing the default value of .Spec.SnapshotMaxCount, Longhorn applies the value of the snapshot-max-count setting. Changing the value of snapshot-max-count does not affect existing volumes.

snapshot-count-warning-threshold: The warning threshold for the count-based TooManySnapshots condition.

You must specify a value between 2 and 250. The default value is 100.

When the number of snapshots on a volume reaches this threshold, Longhorn sets the TooManySnapshots condition. This threshold is independent of the hard limit enforced by snapshot-max-count. See Count-Based Threshold.

Volume-Specific Settings

SnapshotMaxCount: Maximum number of snapshots that you can create for a specific volume.

You can specify “0” or any value between “2” and “250”. The default value is “0”.

When you create a volume without changing the default value of this setting, Longhorn applies the value of the snapshot-max-count setting.

This value also serves as the upper bound for the TooManySnapshots condition when the value is greater than 0. See TooManySnapshots Condition.

SnapshotMaxSize: Maximum aggregate size of snapshots for a specific volume.

You can specify “0” or any value larger than Volume.Spec.Size multiplied by 2. You must double the value of Volume.Spec.Size because Longhorn requires at least two snapshots to function properly.

The default value is “0”, which effectively disables the setting.

When you expand the volume size, Longhorn automatically increases the value of this setting to Volume.Spec.Size multiplied by 2 (if the current value is smaller).

When SnapshotMaxSize is set to a non-zero value, Longhorn also uses it as the threshold for the TooManySnapshots condition. See TooManySnapshots Condition.

TooManySnapshots Condition

Longhorn sets the TooManySnapshots volume condition when snapshot usage approaches or exceeds the configured limits. The condition is evaluated against two independent thresholds.

Notice:

Removed snapshots, backing images, and the volume head are excluded from both calculations.

Count-Based Threshold

The condition is set when the number of snapshots reaches or exceeds the effective count threshold.

The effective threshold is min(snapshot-count-warning-threshold, SnapshotMaxCount), where SnapshotMaxCount is the volume-specific hard limit (populated from snapshot-max-count when not explicitly set). This ensures that the warning does not trigger above the hard limit.

For example, with the default settings (snapshot-count-warning-threshold = 100, snapshot-max-count = 250), the condition is triggered when a volume reaches 100 snapshots, well before the hard limit is reached. If you lower SnapshotMaxCount on a specific volume to 50, the effective threshold becomes 50.

Size-Based Threshold

The condition is set when the total size of all snapshots reaches or exceeds the SnapshotMaxSize value.

This threshold is only active when SnapshotMaxSize is set to a non-zero value. When SnapshotMaxSize is 0 (the default), size is not evaluated.

Combined Warnings

Both thresholds are evaluated independently during each reconciliation. When both are exceeded simultaneously, the condition message includes a description for each reason, separated by a semicolon.