Logically group EC2 instances
Cluster Placement Group
- Grouping of instances within a single availablity zone
- Recommended for applications that need low network latency, high network throughput, or both (HPC)
- Only certain instance types can be launched into a cluster group
- Cluster placement groups can't span mulitple availablity zones
Spread Placement Group
- Group of instances placed on distinct underlying hardware
- Recommended for applications that have a small number of critical instances that should be kept seperate from each other
- Use for individual instances
- Spread placement groups can span multiple availablity zones
Partition Placement Group
- Each partion placement group has it's own set of server rack
- Each rack has it's own network and power source
- No two partions share the same rack, allow you to isolate the impact of a hardware failure within a application
- EC2 logically divides each group into logical segments called partitions
- Used for multiple instance with dedicated network and power sources
Other notes
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Only certain instance types can be launched into a placement group
- Compute optimized
- GPU
- Memory optimized
- Storage optimized
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Placement groups can't be merged
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AWS recommneds homogenous instances within a cluster placement group
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Existing instances can be moved into a placement group if they are in a stopped state
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Instance in placement groups can be removed via the AWS CLI or SDK (not console)