051 placement groups
Strategies
Cluster
- single AZ (not single rack)
- high per-flow throughput limit for TCP/IP
For
- Apps that benefit from low network latency, high network throughput or both
- when the majority of the traffic is between the instances in group
Limit:
- using the same instance type for all instances is recommended.
Partition
spread across different partition
- each partition within a placement group has its own set of racks
For:
- large distributed and replicated workloads, such as HDFS, HBase, and Cassandra, across distinct racks
Limit:
- maximum of seven partitions per Availability Zone
Spread
spread across different hardware (rack)
- reduces the risk of simultaneous failures that might occur when instances share the same equipment
For:
- mix instance types
- launch instances over time
Limit:
- up to 7 instances per AZ (no multiple region)