EC2 Placement Groups

Question 1

Normally, when you launch an instance in AWS, fo you select where it will be placed physically within a datacenter?

Answer 1

No. AWS chooses the EC2 host that is the best for you based on the AZ where you are launching the instance on.

Question 2

What is the main advantage of Cluster placement groups?

Answer 2

• It packs instances close together, with this, it achieves the highest level of performance possible in EC2.
• Cluster placements need to take part within the same AZ.
• All members have direct connections to each other
• 10 Gbps single stream (vs 5 Gbps normally).
• Lowest latency and max PPS (packets per second) possible in AWS - you have to use enhanced networking in all the instances as prerequirement to be high performant.

Question 3

With Cluster placements groups, where are the instances normally placed?

Answer 3

Generally in the same rack but they could even be placed in the same EC2 host.

Question 4

How much t-put in a single stream can you achieve using cluster placement groups?

Answer 4

10 Gbps single stream vs 5 Gbps normally.

Question 5

Describe the disadvantages of using cluster placement groups:

Answer 5

If the HW fails, the entire cluster will fail.

Question 6

Can you use Cluster placement groups in multiple AZs?

Answer 6

No, ONE AZ ONLY. The first AZ used will lock down the cluster to that AZ.

Question 7

Do Cluster placement groups require special instance types?

Answer 7

Yes, not all the instance types are supported for cluster placement groups.

Question 8

What is the best practice when lauching instances using Cluster placement groups?

Answer 8

• Use the same instance type.

- Launch all the instances at once (not mandatory)

Question 9

What could happen if you do not launch all the instances in a cluster placement group at the same time?

Answer 9

You could get an error related with capacity when you are adding additional instances.
If this happens, you can stop all the instances and run them at the same time in another placement group.

Question 10

What is the only way of achieving 10 Gbps of performance in a single stream?

Answer 10

Using cluster placement groups

Question 11

What is the main purpose of using spread placement groups?

Answer 11

Keep instances separated = makes sure that the intances use diffent underlazing hardware.

Question 12

What are Spread placement groups designed for?

Answer 12

This placement group is designed to provide the best resilience and availability for an application.

Question 13

What are Cluster placement groups designed for?

Answer 13

Achieves the highest level of performance possible in EC2.

• Low latency, max PPS (packets per second) and best performance in a single stream (10 Gbps).

Question 14

Can you span Cluster Placement groups in multiple AZs?

Answer 14

No. Only in one AZ

Question 15

Can you span Spread placement groups in multiple AZs?

Answer 15

Information will be put on distinct racks with their own network or power supply

Question 16

Is there a limit of how many instances can you launch per AZ when using Spread placement groups? What do you achieve?

Answer 16

Yes, 7 instances per AZ.

It ensures that a failure in a rack will not affect the rest of the placement group.

Question 17

What do Spread placement groups provide?

Answer 17

HIghest level of availability and resilience. Each instance runs in a different rack by default

Question 18

Are spread placement groups supported by dedicated instances or dedicated hosts?

Answer 18

No.

Question 19

Describe use cases of Spread placement groups:

Answer 19

• Small number of critical instances that need to be kept separated from each other
• Several mirrors of an application

Question 20

Define Partition placement groups

Answer 20

it is a placement group that defines groups of instances spread apart, each group is in a different HW.

Question 21

What is the main difference between Spread and Partition placement groups?

Answer 21

The main difference is you can launch as many instances in each partition
as you desire.

Question 22

How many partitions (groups) can you create per AZ?

Answer 22

7 partitions maximum per AZ.

Question 23

Where can instances be places when using partitions placement groups?

Answer 23

They can be places in specific partitions or autoplaced by AWS.

Question 24

Are partitions placement groups supported on Dedicated hosts?

Answer 24

No.