EC2 Placement groups

Related: EC2, Scaling

• Cluster – instances use one hardware
  • Best practice to use same type of instances and to deploy all needed instances from the start for capacity evaluation.
  • Same rack, sometimes same host.
  • Fastest inter-instance networking, you probably require network instance types. Up to 10 Gbps per single stream.
  • One AZ only, VPC peers can be spanned.
  • Best for fast speeds/low latency, where no resilience is acceptable
    
• Spread – instances use different hardware
  • Cross-AZ, instances are spread access AZ, so AZ-failure resilient
  • Max 7 Instances per AZ
  • Infrastructure isolation, each instance within spread placement group runs from a different rack, each rack has it’s own power and network supply
  • Small number of critical instances, with AZ level resilience and needs to be separated from each other. Like fileshares.
  • You don’t manage in which racks to place instances.
    
• Partitioned – groups of instances on different hardware
  • Designed for more than 7 instances per AZ.
  • Uses multiple partitions up to 7 instances each within AZ
  • Each partition has it’s own rack, so partitions separated.
  • You select into which partition launch an instance.
  • Best for huge scale parallel processing. Can be used with topology aware applications such as HDFS, HBase and Cassandra (intelligent data replication)