Skip to main content

EC2 Exam Notes

1. Overview of Amazon EC2​

  • Definition:
    EC2 (Elastic Compute Cloud) is AWS’s Infrastructure as a Service (IaaS) offering that gives you scalable virtual servers in the cloud.
  • Key Benefits:
    • On-demand scalability
    • Flexible configurations
    • Integration with other AWS services

2. EC2 Instance Types​

AWS categorizes instances based on the workload they best support:

  • General Purpose:

    • Usage: Versatile for tasks like hosting web servers or code repositories
    • Example: An M5 instance can handle balanced CPU, memory, and networking needs.

  • Compute Optimized:

    • Usage: Ideal for compute-intensive tasks that require high-performance processors
    • Example: A C5 instance is great for batch processing and high-performance web servers.

  • Memory Optimized:

    • Usage: Best for workloads processing large data sets in memory (e.g., in‑memory databases)
    • Example: R5 or R6 instances are tailored for memory-bound applications.

  • Storage Optimized:

    • Usage: Designed for tasks requiring high, sequential read/write access to local storage
    • Example: I3 instances are used for high-performance storage tasks.

Note: Some exam questions might also reference Accelerated Computing (e.g., GPU instances) even though they aren’t listed in your notes.

3. Security Groups​

  • Concept:
    Security groups act as a virtual firewall controlling traffic to and from your EC2 instances.
  • Default Behavior:
    • Inbound: All traffic blocked by default
    • Outbound: All traffic allowed by default
  • Characteristics:
    • They contain only allow rules (no deny rules).
    • A single security group can be attached to multiple instances within the same AWS Region/VPC.

Example:
When configuring a web server, you might add an allow rule for HTTP (port 80) and HTTPS (port 443) while leaving all other inbound traffic blocked.

4. EC2 Purchasing Options​

AWS offers several pricing models to match various workload requirements:

  • On-Demand Instances:

    • Characteristics:
      • No long-term commitment
      • Highest cost per hour
    • Best for:
      • Short-term, unpredictable, or uninterruptible workloads

  • Reserved Instances:

    • Reservation Period: 1 year or 3 years
    • Payment Options:
      • No Upfront
      • Partial Upfront
      • All Upfront
    • Best for:
      • Steady-state workloads that run continuously
    • Convertible Reserved Instances:
      • Allow you to change the instance type during the reservation period

  • Savings Plans:

    • Overview:
      • Commit to a certain usage (1 or 3 years) to get a discount
    • Best for:
      • Organizations with predictable, long-term usage

  • Spot Instances:

    • Characteristics:
      • Most cost-efficient (up to 90% discount)
      • Can be interrupted by AWS with little notice
    • Best for:
      • Distributed, flexible workloads that are fault-tolerant

  • Dedicated Hosts:

    • Overview:
      • A physical server dedicated solely to your use
      • Supports strict compliance requirements and complex software licenses
    • Cost:
      • The most expensive option

  • Dedicated Instances:

    • Overview:
      • Run on hardware dedicated to your account but might share that hardware with other instances from your account

  • Capacity Reservations:

    • Purpose:
      • Guarantee access to EC2 capacity when you need it
    • Best for:
      • Short-term, uninterrupted workloads