# Amazon Elastic File System
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To use an existing external Amazon EFS file system for long-term permanent storage outside of the cluster life cycle, specify [`EfsSettings`](SharedStorage-v3.md#SharedStorage-v3-EfsSettings) / [`FileSystemId`](SharedStorage-v3.md#yaml-SharedStorage-EfsSettings-FileSystemId), by default, Amazon ParallelCluster creates a managed Amazon EFS file system from [`EfsSettings`](SharedStorage-v3.md#SharedStorage-v3-EfsSettings) when it creates the cluster. Amazon ParallelCluster also deletes the file system and data when the cluster is deleted or when the file system is removed from the cluster configuration.

For an Amazon ParallelCluster managed Amazon EFS file system, you can use the [`EfsSettings`](SharedStorage-v3.md#SharedStorage-v3-EfsSettings) / [`DeletionPolicy`](SharedStorage-v3.md#yaml-SharedStorage-EfsSettings-DeletionPolicy) to instruct Amazon ParallelCluster to `Delete` or `Retain` either when the cluster is deleted or when the file system removed from the cluster configuration. By default, `DeletionPolicy` is set to `Delete`.

**Warning**  
For Amazon ParallelCluster managed shared storage, `DeletionPolicy` is set to `Delete` by default.  
This means that, if one of the following is true, a managed file system and its data are deleted:  
You delete the cluster.
You change the managed shared storage configuration [`SharedStorage`](SharedStorage-v3.md) / [`Name`](SharedStorage-v3.md#yaml-SharedStorage-Name).
You remove the managed shared storage from the configuration.
We recommend that you back up your shared storage regularly to avoid the loss of data. For more information about how to back up individual Amazon EFS volumes, see [Backing up your Amazon EFS file systems](https://docs.amazonaws.cn/efs/latest/ug/efs-backup-solutions.html) in the *Amazon Elastic File System User Guide*. To learn how to manage data backups across Amazon Web Services services, see [Amazon Backup](https://docs.amazonaws.cn/aws-backup/latest/devguide/whatisbackup.html) in the *Amazon Backup Developer Guide*.