EC2 architecture and resilience

Question 1

What are EC2 instances?

Answer 1

EC2 instances are virtual machines run on EC2 hosts

Question 2

What types of hosts are used in EC2?

Answer 2

Shared hosts: every customer is isolated even on the same shared hardware.
Dedicated hosts: pay for the entire hardware, don’t pay for instances.

Question 3

What level of resilience does EC2 provide?

Answer 3

AZ resilient service. They run within only one AZ system.

Question 4

Can you access instances in a cross zone way?

Answer 4

You can’t access them cross zone.

Question 5

What does an EC2 host contain?

Answer 5

• Local hardware such - CPU and memory
• Also have a temporary instance storage (If instance moves hosts, the storage is lost)
• Can use remote storage, Elastic Block Store (EBS)

Question 6

What is EBS used for in EC2 instances?

Answer 6

• EBS allows you to allocate volumes of persistent storage to instances within the same AZ.

Question 7

What types of networking exist in EC2?

Answer 7

• 2 types of networking
  
  • Storage networking
  • Data networking

Question 8

When do EC2 instances get ENIs assigned to them?

Answer 8

When the EC2 instances are created and provisioned within a specific subnet.

Question 9

What is the function of ENIs?

Answer 9

It maps to the physical hardware on the EC2 host.

Question 10

Can instances have multiple network interfaces?

Answer 10

Yes

Question 11

Can EC2 instances have multiple interfaces in multiple subnets?

Answer 11

Yes, as long as the subnets are in the same AZ.

Question 12

An instance runs on a specific host. If you restart the instance…what happens?

Answer 12

The instance stays in the host.

Question 13

When will an EC2 instance leave the host where it is running?

Answer 13

• The host fails or is taken down by AWS - maintenance

- The instance is stopped and then started, different than restarted.

Question 14

When an EC2 instance is moved from its host, where is it relocated?

Answer 14

To another host in the same AZ.

Question 15

What is a migration of an EC2 instances?

Answer 15

It is taking a copy of an instance and moving it to a different AZ.

Question 16

In which cases is EC2 useful?

Answer 16

Long running compute needs like server style applications

Question 17

Mention some server style applications where EC2 is useful:

Answer 17

• things waiting for network response
• long running compute
• traditional OS+Application compute
• burst or steady-state load
• monolithic application stacks
  
  • middle ware or specific run time components
• migrating application workloads or disaster recovery
  
  • existing applications running on a server and a backup system to intervene

Question 18

The instance types will variate depending on:

Answer 18

• Raw CPU, memory, local storage, capacity & type
• Resource ratios
• Storage and data network bandwidth
• System architecture / Vendor
• Additional features and capabilities - GPUs, FPGAs

Question 19

What are the main instance categories/types in EC2?

Answer 19

• General-purpose
• Compute-optimized
• Memory-optimized
• Accelerated computing
• Storage optimized

Question 20

When should you use General purpose type instances?

Answer 20

Default steady-state workloads with even resources.

Question 21

When should you use Compute-optimized type instances?

Answer 21

Media processing, scientific modeling and high-performance computing, gaming, machine learning.

Provides the latest high-performance CPUs with a higher ratio of CPU over the memory for a given price point.

Question 22

When should you use Memory Optimized type instances?

Answer 22

perfect for processing large in-memory data sets, in-memory caching, database workloads

Question 23

What does the Accelerated-computing instances offer?

Answer 23

Hardware GPU, FPGAs. Dedicated GPUs, high-scale parallel processing and modeling, custom programmable hardware such as FPGAs

Question 24

When should you use Storage optimized type instances?

Answer 24

Large amounts of super fast local storage. Massive amounts of IO per second. Scale-out transactional databases, data warehousing, Elastic search, and analytic workloads.

Designed for high sequential transfer rates

Question 25

How is the instance type naming scheme in EC2? R5dn.8xlarge

Answer 25

• 1st char: Instance family.
• 2nd char: Instance generation. Generally always select the newest generation.
• 3rd char - before period: additional capabilities
  
  • a: amd cpu
  • d: NVMe storage
  • n: network optimized
  • e: extra capacity for ram or storage
• char after period: Instance size. Memory and CPU considerations.
  
  • It is often easier to scale a system with a larger number of smaller instance sizes.