What is a “placement group”?
A placement gruop is a logical grouping of instances within a single AZ. Using placement groups make it possible for applications to take part in a low latency, 10 Gbps NW. Placement groups are necessary for applications that benefit from low network latency, high network throughput.
Features
A placement groups cannot span mutiple AZ
The name you specify for a placement group must be unique within you AWS account
Only particular types of instances can be launched in a placement group like compute optimized, GPU, memory optimized, storage optimized
AWS recommend homogenous instances within placement roups.(same size, same famaily)
Merging placement groups is not possible
Can’t move a running instance into another group.
Rather create an AMI from the running intance then launch a new intance from the AMI into a placement group.
