Creates a new, empty file system. The operation requires a creation token in the request that Amazon EFS uses to ensure idempotent creation (calling the operation with same creation token has no effect). If a file system does not currently exist that is owned by the caller's AWS account with the specified creation token, this operation does the following:

Creates a new, empty file system. The file system will have an Amazon

EFS assigned ID, and an initial lifecycle state creating.

Returns with the description of the created file system.

Otherwise, this operation returns a FileSystemAlreadyExists error with

the ID of the existing file system.

For basic use cases, you can use a randomly generated UUID for the creation


The idempotent operation allows you to retry a CreateFileSystem call without

risk of creating an extra file system. This can happen when an initial call fails in a way that leaves it uncertain whether or not a file system was actually created. An example might be that a transport level timeout occurred or your connection was reset. As long as you use the same creation token, if the initial call had succeeded in creating a file system, the client can learn of its existence from the FileSystemAlreadyExists error.

The CreateFileSystem call returns while the file system's lifecycle state

is still creating. You can check the file system creation status by calling the DescribeFileSystems operation, which among other things returns the file system state.

This operation also takes an optional PerformanceMode parameter that you

choose for your file system. We recommend generalPurpose performance mode for most file systems. File systems using the maxIO performance mode can scale to higher levels of aggregate throughput and operations per second with a tradeoff of slightly higher latencies for most file operations. The performance mode can't be changed after the file system has been created. For more information, see Amazon EFS: Performance Modes (

After the file system is fully created, Amazon EFS sets its lifecycle state to available, at which point you can create one or more mount targets for the file system in your VPC. For more information, see CreateMountTarget. You mount your Amazon EFS file system on an EC2 instances in your VPC via the mount target. For more information, see Amazon EFS: How it Works (

This operation requires permissions for the elasticfilesystem:CreateFileSystem