Your organization has an existing VPC in us-east-1 with two subnets in us-east-1b. They are running few EC2 instances each in both subnets and would need a low latency common File
Store for all instances to share files for heavy workloads. They have created an EFS, mounted on all the EC2 instances, and share files across all the EC2 instances. You were tasked to increase the number of instances due to the increase in workload. You created a new subnet in us-east-1c and launched a few instances. When you tried to mount the previously created EFS on new EC2 instances, the operations fail. What could be the reason?
 

Answer options:

A.AWS EFS does not support cross availability zone mounting.
B.By default, EFS is only available in one availability zone. Create a case with AWS support to increase EFS availability zones.
C.EFS created with mount targets in an us-east-1b availability zone. Instances in us-east-1c cannot use the EFS mount target in us-east-1b.
D.EFS mount target security group inbound rules do not allow traffic from new EC2 instances.

Answer: D
Amazon EFS provides scalable file storage for use with Amazon EC2. You can create an EFS file system and configure your instances to mount the file system. You can use an EFS file system as a common data source for workloads and applications running on multiple instances.
For options A, B, C, EFS mount targets from one availability zone can be mounted on another availability zone, although this approach is not recommended. However, this approach will not cause operations to fail.
Creating or Deleting Mount Targets in a VPC
A VPC peering connection is a networking connection between two VPCs that enables you to route traffic between them using private Internet Protocol version 4 (IPv4) or Internet Protocol version 6 (IPv6) addresses. For more information on VPC peering, see What is VPC Peering? in the Amazon VPC Peering Guide.
You can mount Amazon EFS file systems over VPC connections by using VPC peering within a single AWS Region when using the Amazon EC2 instance types T3, C5, C5d, I3.metal, M5, M5d, R5, R5d, and z1d. However, other VPC private connectivity mechanisms such as inter-region VPC peering and VPC peering within an AWS Region using other instance types are not supported.
Note the following restrictions:
You can mount an Amazon EFS file system on instances in only one VPC at a time.
Both the file system and VPC must be in the same AWS Region.
For option D, when using Amazon EFS, you specify Amazon EC2 security groups for the EFS mount targets associated with the file system. Security groups act as a firewall, and the rules you add define the traffic flow.
You can authorize inbound and outbound access to your EFS file system. To do so, you add rules that allow your EC2 instance to connect to your Amazon EFS file system through the mount target using the Network File System (NFS) port.