Placement groups in AWS

When you launch an EC2 instance on AWS, it is placed within the vast infrastructure of AWS using a concept called Placement Groups. Placement Groups are a strategic approach that allocates your EC2 instances across the underlying hardware.

There are three main strategies for placement groups, each suited for different types of workloads:

1. Cluster: With the cluster strategy, instances are tightly packed together within a single Availability Zone (AZ). This placement allows for low-latency network performance, which is beneficial for tightly-coupled applications. High-performance computing apps that require minimal latency often benefit from this strategy.

2. Partition: The partition strategy involves spreading instances across logical partitions, ensuring that instances in one partition do not share underlying hardware with instances in different partitions. Instances are placed in separate racks within a zone, reducing the risk of hardware failure impacting multiple instances. This strategy is commonly used for large distributed workloads and replicated systems, where data is replicated on multiple nodes.

3. Spread: The spread strategy distributes a small group of EC2 instances across distinct underlying hardware to minimize the impact of correlated failures. By placing instances on separate hardware, this strategy enhances fault tolerance. It is considered the safest approach for placing EC2 instances on the underlying hardware.

By leveraging placement groups, you can optimize the performance, availability, and fault tolerance of your EC2 instances by controlling how they are positioned within the AWS-managed hardware. This enables you to align the placement with the specific requirements of your workloads and ensure efficient utilization of resources.