EC2 Placement Groups Flashcards
What are the three types of Placement Groups?
Cluster, Spread and Partition
What’s the primary goal of Cluster placement groups?
To ensure that EC2 instances are physically close together
What are the two performance benefits of Cluster placement groups?
Higher speeds and lower latency
Can you configure which AZ a Cluster placement group is deployed into?
No.
AWS decides the AZ at launch time, based on the first instance that’s launched.
How do you change the AZ that a Cluster placement group is in?
You can’t. Once the first VM is deployed, its placement group is locked to that single AZ.
How many AZs can a Cluster placement group span?
One.
What is the maximum data transfer rate between hosts in a Cluster placement group, and how is this limit expressed?
It is 10 Gbps per 5-tuple (also known as single-stream). This is double the normal limit of 5 Gbps.
Is it possible to span a Cluster placement group across VPC peers, and if so, what impact does it have?
Yes. But doing so impacts performance.
Cluster placement groups must use ………… instance types
Supported
Can you use mixed EC2 instance types within in a Cluster placement group.
Yes, but it is recommended to use the same instance type for all members.
What is the recommended way to launch instances in a Cluster placement group? Why is this?
It is strongly recommended to launch all instances at the same time.
This allows AWS to choose hardware that has room for all of your instances.
What’s the primary goal of Spread placement groups?
To provide infrastructure isolation, spreading your instances across distinct underlying hardware to reduce correlated failures.
How do Spread placement groups achieve their goal?
By running each instance from a different rack, with each rack having its own network and power source.
With Spread placement groups, there is a max limit of …… instances per ……….
Max of 7 instances per AZ.
Spread placement groups <can|cannot> span multiple AZs?
They can.
What class of instances are NOT supported in Spread placement groups?
Dedicated instances and Dedicated hosts are not supported. Only shared instances are supported.
What is the typical use case for Spread placement groups?
Critical workloads that require high availability and reliability.
What is the ideal placement group type for critical workloads that require high availability and reliability?
Spread placement groups.
How do Partition placement groups achieve their goal?
Instances are placed into partitions, which have their own power and network connectivity. If there’s a failure in one partition, only the instances within that partition will be affected.
In a Partition placement group, what determines which partition an instance is placed into?
The user can choose, or AWS can auto-assign.
What is the typical use case for Partition placement groups?
Large distributed and replicated workloads, such as big data applications or large-scale distributed databases. Think HDFS, HBase, Cassandra.
What is the ideal placement group type for large distributed and replicated workloads, such as big data applications or large-scale distributed databases?
Partition placement groups.
What is the ideal placement group type for HDFS, HBase or Cassandra?
Partition placement groups.
