EC2 placement groups

Topic: Cloud aws core

Placement groups control how instances are placed: cluster for low latency, spread for isolation, partition for large distributed apps. Use when you need low latency or fault isolation.

Intent: How-to

Quick answer

  • Cluster: instances close together for low latency. Single AZ. Good for HPC or tightly coupled. Risk of correlated failure.
  • Spread: one instance per rack. Maximize isolation. Good for critical instances. Limited instances per group per AZ.
  • Partition: groups of instances in partitions. For large distributed systems (e.g. Kafka, HDFS). Partition failure does not take whole group.

Prerequisites

Steps

  1. Choose strategy

    Cluster for low latency. Spread for isolation. Partition for large distributed apps.

  2. Create placement group

    EC2 Placement Groups. Create. Choose type. Name. Create.

  3. Launch in group

    Launch instance. Select placement group. Or add to group when launching. Same type for cluster.

Summary

Placement groups control placement: cluster for low latency, spread for isolation, partition for large distributed apps.

Prerequisites

Steps

Step 1: Choose strategy

Cluster for low latency. Spread for isolation. Partition for large distributed apps.

Step 2: Create placement group

EC2 Placement Groups. Create. Choose type and name.

Step 3: Launch in group

Launch instance. Select placement group. Same type for cluster.

Verification

  • Instances in placement group. Placement type as chosen.

Troubleshooting

Capacity — Try another AZ or size. Wrong type — Cluster often requires same instance type.

Next steps

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