Placement Group

Before going to the explanation part of placement groups in AWS first let me tell about general meaning

  • the groups is nothing but gathering together

  • placement is nothing but placing the things at one point of place

So overall meaning is placing the things at one place or gathering the things together at one place is nothing but placement groups.

Now, let’s get into the actual definition of placement groups, placement groups is a way of logical grouping of interdependent instances together in a selected region, or in other words as the name implies, a placement group is just a group. AWS instances that exist within a common availability zone can be grouped into a placement group. Where group members are able to communicate with one another in a way that provides low latency and high throughput.

What is the low latency?

Low latency means the faster transfer of traffic rate between the customer and the application or in other words it is defined as the end-to-end latency from the moment a record is written to the stream until it is read by a consumer application and this delay varies depending upon a number of factors, but it is primarily affected by the polling interval of consumer applications.

What is the high thruput?

High Throughput is the measure of the amount of data transferred from/to a storage device in a second. Typically stated in KB/MB/GB/s (e.g., if a storage device can write 1000 blocks of 128K each, throughput is 1000*128K/s = 128MB/s).

All nodes within the placement group can talk to all other nodes within the placement group at the full line rate of 10 Gbps single traffic flow without any slowing due to over-subscription.

Placement groups helps us to launch bunch of EC2 instances close to each other physically within the same AZ . Being close physically and within the same AZ helps it take advantage of high speed connectivity to provide low latency, high throughput access.

This can really work well for applications exchanging lot of data and can provide high performance with collocation.

All nodes within the placement group can talk to all other nodes within the placement group at the full line rate of 10 Gbps single traffic flow without any slowing due to over-subscription.

When to use Placement Group?

When applications reaching over subscriptions or when there is a high latency etc.

Types of Placement Group?

We can create a placement group using one of the following placement strategies:

  • Cluster Placement Group: Packs instances close together inside an Availability Zone. This strategy enables workloads to achieve the low-latency network performance necessary for tightly-coupled node-to-node communication that is typical of HPC applications.

  • Partition Placement Group: Spreads your instances across logical partitions such that groups of instances in one partition do not share the underlying hardware with groups of instances in different partitions. This strategy is typically used by large distributed and replicated workloads, such as Hadoop, Cassandra, and Kafka.

  • Spread Placement Group: Strictly places a small group of instances across distinct underlying hardware to reduce correlated failures.

Source: AWS Placement Group