EC2

Tenancy Placement

Tenancy defines how EC2 instances are distributed across physical hardware and affects pricing. There are three tenancy options available:

• Shared (default) — Multiple AWS accounts may share the same physical hardware.

• Dedicated Instance (dedicated) - Ensures all EC2 instances that are launched in a VPC run on hardware that's dedicated to a single customer ( Dedicated Instances may share hardware with other instances from the same AWS account that are not Dedicated Instances).

• Dedicated Host (host) — Your instance runs on a physical server with EC2 instance capacity fully dedicated to your use, an isolated server with configurations that you can control (To use a tenancy value of host, you must use a launch template).

VPC tenancy

When you create a launch configuration, the default value for the instance placement tenancy is null and the instance tenancy is controlled by the tenancy attribute of the VPC.

Note that:

• Some AWS services or their features won't work with a VPC with the instance tenancy set to dedicated.
• Some instance types cannot be launched into a VPC with the instance tenancy set to dedicated.

Placement Group

• Cluster groups launch each associated instance into a single availability zone within close physical proximity to each other. This provides low-latency network interconnectivity and can be useful for high-performance computing (HPC) applications, for instance.

• Spread groups separate instances physically across distinct hardware racks and even availability zones to reduce the risk of failure-related data or service loss. Such a setup can be valuable when you’re running hosts that can’t tolerate multiple concurrent failures.

• Partition groups is in the middle, that places a small group of instances across distinct underlying hardware to reduce correlated failures. Partition placement groups can be used to deploy large distributed and replicated workloads, such as HDFS, HBase, and Cassandra, across distinct racks.

Enhanced Networking

Enhanced networking uses single root I/O virtualization (SR-IOV) to provide high-performance networking capabilities on supported instance types. SR-IOV is a method of device virtualization that provides higher I/O performance and lower CPU utilization when compared to traditional virtualized network interfaces. Enhanced networking provides higher bandwidth, higher packet per second (PPS) performance, and consistently lower inter-instance latencies. There is no additional charge for using enhanced networking.

Elastic Fabric Adapter (EFA)

• EFA OS-bypass traffic is limited to a single subnet. In other words, EFA traffic cannot be sent from one subnet to another. Normal IP traffic from the EFA can be sent from one subnet to another.

• EFA OS-bypass traffic is not routable. Normal IP traffic from the EFA remains routable.

• The EFA must be a member of a security group that allows all inbound and outbound traffic to and from the security group itself.

Differences between EFAs and ENAs

• Elastic Network Adapters (ENAs) provide traditional IP networking features that are required to support VPC networking.
• EFAs provide all of the same traditional IP networking features as ENAs, and they also support OS-bypass capabilities. OS-bypass enables HPC and machine learning applications to bypass the operating system kernel and to communicate directly with the EFA device.

Lifecycle hook

Elastic IP address

An Elastic IP address doesn’t incur charges as long as the following conditions are true:

• The Elastic IP address is associated with an Amazon EC2 instance.
• The instance associated with the Elastic IP address is running.
• The instance has only one Elastic IP address attached to it.

Read More:

• Configuring instance tenancy with a launch configuration
• Placement Group