Amazon EFS is AWS version of Managed NFS (network file system) and can be mounted on multiple EC2 instance to provide shared storage.   Additionally EFS can work with EC2 Instance in multiple Availability Zones.  It provides for high availability and is scalable but it is 3x more expensive than a gp2 storage. Characteristics of EFS are:

        1.  Use case: Content Management, Web Servers, Data Sharing, WordPress sites.

        2.  Uses NFSv4.1 protocol

        3.  Security group must be setup to control access to EFS

        4.  Only compatible with Linux AMI, no Windows.

        5.  Supports encryption with KMS.

        6.  POSIX file system (Linux) with standard API.

        7.  Scales automatically, no capacity planning required.

        8.  Only pay for storage you actually use.

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Three Types of EFS

        1.  Scale Mode

                a.  1000s of concurrent NFS clients with 10GB+/s throughput.

                b.  Can grow to Petabyte-scale NFS, automatically.

        2.  Performance Mode

                a.  General purpose – for latency sensitive uses.

                b.  Max I/O – high latency, throughput, hight parallel

        3.  Throughput Mode

                a.  Bursting to 50MiB/s to 100MiB/s

                b.  Provisioned – set throughput regardless of overall size.

                c.  Elastic – automatically scales throughput up and down base on workload.

                        i.  Max 3GiB/s read and 1GiB/s writes.

                        ii.  Used for unpredictable workloads.

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EFS 3 Storage Tiers – Lifecycle policies govern moving between tiers

        1.  Standard – for frequently accessed data.

        2.  Infrequent Access (EFS-IA) – low storage cost, but cost to retrieve data.

        4.  Archive – data accessed a few times a year, 50% cheaper storage.

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EFS Availability

        1.  Standard – multiple Availability Zone

        2.  One Zone – restricted to single Availability Zone (Dev or Test system)