# Buffer

Previously defined in the [Buffering](https://docs.fluentbit.io/manual/3.0/concepts/buffering) concept section, the `buffer` phase in the pipeline aims to provide a unified and persistent mechanism to store your data, either using the primary in-memory model or using the filesystem based mode.

The `buffer` phase already contains the data in an immutable state, meaning, no other filter can be applied.

{% @mermaid/diagram content="graph LR
accTitle: Fluent Bit data pipeline
accDescr: The Fluent Bit data pipeline includes input, a parser, a filter, a buffer, routing, and various outputs.
A\[Input] --> B\[Parser]
B --> C\[Filter]
C --> D\[Buffer]
D --> E((Routing))
E --> F\[Output 1]
E --> G\[Output 2]
E --> H\[Output 3]
style D stroke:darkred,stroke-width:2px;" %}

{% hint style="info" %}
Note that buffered data is not raw text, it's in Fluent Bit's internal binary representation.
{% endhint %}

Fluent Bit offers a buffering mechanism in the file system that acts as a *backup system* to avoid data loss in case of system failures.