Section 5/6: EC2 Fundamentals & Solutions Architecture

Question 1

What are the four EC2 pricing models?

Answer 1

1) On demand
2) Reserved
3) Spot
4) Dedicated host

Question 2

Cheapest EC2 pricing?

Answer 2

Spot instances (up to 90% discount)

Question 3

EC2 Spot Instance use cases

Answer 3

Stateless workloads resilient to failures like big data / data analysis

Question 4

What are EC2 Spot Instances?

Answer 4

Bidding on capacity that isn’t being used & can be kicked off if someone bids higher.
Define the max spot price and get the instance when current spot price is below your max spot price.

Question 5

What are spot instances not good for?

Answer 5

DBs, critical jobs or any persistent workloads

Question 6

What are the four types of EC2 instances?

Answer 6

1) general purpose
2) Compute optimized
3) Memory Optimized
4) Storage optimized

Question 7

Why use a General purpose EC2 instance?

Answer 7

• Diversity of workloads (web servers / code repos)
• Balance between compute, memory, networking

Question 8

Why use a Compute Optimized EC2 instance?

Answer 8

• great for compute intensive tasks
• high performance computing, ML, modeling

Question 9

Why use a Memory Optimized EC2 instance?

Answer 9

• For storage intensive tasks
• Databases, data warehousing, caching

Question 10

What are the two types of spot fleet termination requests?

Answer 10

1) One-time request
2) Persistent Request

Question 11

What is a one-time Spot Fleet termination request?

Answer 11

If current spot price > max price you can choose to stop or terminate instance with a 2 minute grace period
Persistent request

Question 12

What is a persistent-request Spot Fleet Termination Request?

Answer 12

Terminate instance, but as soon as the spot price goes back below your spot price, the instance is going to get relaunched

Question 13

Identifying devices using a Public vs Private IP?

Answer 13

Public IPs are used to identify a device outside a network.
Private IPs are used to identify a device within a local network.

Question 14

IPv4 vs IPv6?

Answer 14

IPv4 is older and running out of addresses. IPv6 is newer and solves problems of IPv4

Question 15

When you stop and start an EC2, what happens to it’s IP address?

Answer 15

The EC2 instance’s public IP address can change

Question 16

What is an Elastic IP, and when would we use it?

Answer 16

An Elastic IP is a public IPv4 you own as long as you don’t delete it, and can only be attached to one instance at a time. use an Elastic IP if you want to assign a fixed public IP for your instance.

Question 17

Should you try to avoid using Elastic IP?

Answer 17

Yes, because:
Reflects poor architectural decisions,
Better to use a random public IP and register a DNS name to it,
Or ever better use a Load Balancer and don’t use a public IP

Question 18

What is an ENI?

Answer 18

Elastic Network Interface, a virtual netowrk card that automatically attaches to EC2s. Allows primary private IPv4 addresses from address ranges of a VPC. Basic networking.

Question 19

Why use an ENI (elastic network interface) with ENA?

Answer 19

Enhanced networking. ENI’s provide high performance networking capabilities, and should be used when you want good network performance for no additional charge & its available.

Question 20

What is an Elastic Fabric Adapter?

Answer 20

Network device to accelerate High Performance Computing (HPC) and ML operations

Question 21

What are the 3 EC2 Placement Group types?

Answer 21

1) Clustered
2) Spread
3) Partitioned

Question 22

Clustered EC2 placement group: Pros, Cons, Use cases?

Answer 22

Pro: great networking
cons: If the group fails, all instances fail, all instances in singe AZ
Use Cases: 1) Low Network Latency (high network performance)
2) Big data jobs that need to be done quickly
3) Recommended for homogenous instance types

Question 23

Spread EC2 Placement group: Pro’s, Con’s, Use Cases?

Answer 23

Pros: great for critical apps, as each EC2 is placed on distinct underlying physical hardware. Can spam across AZ, reduces risk of simultaneous failure
Cons: Can only run 7 instances per AZ
Use Cases: For apps with small number of critical instances that need to be kept separate, and maximize availability

Question 24

Partitioned EC2 Placement group: Pro’s, Con’s, Use Cases?

Answer 24

Pros: good for distributed apps, as groups are divided into logical segments. Can span multiple AZs in the same region, with 100s of EC2s. Partition failures can affet many EC2s, but not all (isolate hardware failure)
Use Cases: Services that can be partitioned like Cassandra

Question 25

Explain the two EC2 Hibernate options

Answer 25

1) Can stop instances (keeping data intact until next start)
2) Can terminate instances, so any EBS volumes set-up to be destroyed are lost.

Question 26

EC2 Hibernate Limitations

Answer 26

1) Can’t hibernate for more than 60 days
2) Instance RAM must be < 150 GB
3) Can’t hibernate instances in ASG or ECS, doesn’t support all EC2 instance families / AMIs

Question 27

What does an EC2 instance retain from hibernation?

Answer 27

1) Instance ID
2) Private IPv4 Address & all IPv6 Addresses
3) Elastic IPs

Question 28

EC2 Hibernate is..? Use cases?

Answer 28

Hibernate is basically the same as a regular computer hibernating. Use case: Saving Ram State, as hibernate is good for long-running processes that take long to initialize.

Question 29

What is EC2 Nitro, and what does it provide?

Answer 29

Nitro is a new virtualization technology for the next generation of EC2. Provides better performance for EBS, networking, and better underlying security

Question 30

How do you optimize EC2 CPU?

Answer 30

Increase the number of CPU cores and the number of threads per core (1 thread per CPU is useful for HPC workloads)

Question 31

What is EBS?

Answer 31

Elastic Block Storage.
Persistent block storage attached to EC2 instances while they run. Allows instances to persist data even after termination.

Question 32

EBS (elastic block storage) analogy

Answer 32

EBS volumes are “network USB sticks”, not physical drives. They use the netwrok to communicate with the instance, so latency is possible

Question 33

EBS properties

Answer 33

1) Volumes are always in the same AZ as EC2 instance
2) Root EBS volume deleted with instance
3) Can detach volumes as additional disk, without stopping instance.