[Modify/Add] Add ELB, ASG, S3 Doc.

README.md

@@ -17,6 +17,10 @@
   - What is Amazon EC2?, Introduction to Security Groups, Classic Ports to know, EC2 Instance Launch Types, Which purchasing option is right for me?, Shared Responsibility Model for EC2
 - [EC2 Instance Storage](./sections/ec2_storage.md)
   - EBS Volumes, EFS: Elastic File System, EFS Infrequent Access (EFS-IA), Amazon FSx – Overview, EC2 Instance Store, Shared Responsibility Model for EC2 Storage
+- [Elastic Load Balancing & Auto Scaling Groups](./sections/elb_asg.md)
+  - Scalability & High Availability, Vertical Scalability, Horizontal Scalability, High Availability, High Availability & Scalability For EC2, Scalability vs Elasticity (vs Agility), What is load balancing?, What’s an Auto Scaling Group?
+- [Amazon S3](./sections/s3.md)
+  - S3 Use cases, Amazon S3 Overview - Buckets, Amazon S3 Overview - Objects, S3 Websites, S3 Storage Classes, S3 Object Lock & Glacier Vault Lock, Shared Responsibility Model for S3, AWS Snow Family, What is Edge Computing?, Snow Family - Edge Computing, AWS OpsHub, Hybrid Cloud for Storage, AWS Storage Gateway
 
 ## Practice Exams ( dumps )
 

sections/elb_asg.md

@@ -0,0 +1,130 @@
+# Elastic Load Balancing & Auto Scaling Groups
+
+- [Elastic Load Balancing \& Auto Scaling Groups](#elastic-load-balancing--auto-scaling-groups)
+  - [Scalability \& High Availability](#scalability--high-availability)
+  - [Vertical Scalability](#vertical-scalability)
+  - [Horizontal Scalability](#horizontal-scalability)
+  - [High Availability](#high-availability)
+  - [High Availability \& Scalability for EC2](#high-availability--scalability-for-ec2)
+  - [Scalability vs Elasticity (vs Agility)](#scalability-vs-elasticity-vs-agility)
+  - [What is Load Balancing?](#what-is-load-balancing)
+    - [Why Use a Load Balancer?](#why-use-a-load-balancer)
+    - [Why Use an Elastic Load Balancer?](#why-use-an-elastic-load-balancer)
+      - [Types of ELB](#types-of-elb)
+  - [What’s an Auto Scaling Group?](#whats-an-auto-scaling-group)
+    - [Auto Scaling Group Scaling Strategies](#auto-scaling-group-scaling-strategies)
+  - [ELB \& ASG Summary](#elb--asg-summary)
+
+## Scalability & High Availability
+
+- **Scalability**: Ability of a system to handle an increase in load by adapting to the demand.
+- **High Availability**: Ensures a system is operational and accessible for a high percentage of time, often achieved by reducing the impact of failures.
+- There are two kinds of scalability:
+  - Vertical Scalability
+  - Horizontal Scalability (= elasticity)
+- Scalability is linked but different to High Availability
+
+## Vertical Scalability
+
+- Increasing the capacity of a single instance (e.g., moving from t3.medium to t3.large).
+- Suitable for databases or applications where upgrading a single resource is more efficient.
+- Limited by hardware constraints (can only scale up to a certain point).
+
+## Horizontal Scalability
+
+- Adding more instances (servers) to distribute the load across multiple resources.
+- Achieved through technologies like **Auto Scaling Groups (ASG)** and **Elastic Load Balancing (ELB)**.
+- Preferred for applications needing resilience and distributed workloads.
+- Horizontal scaling implies distributed systems.
+
+## High Availability
+
+- Implemented by deploying resources across multiple **Availability Zones** (AZs).
+- Ensures failover and redundancy in case of failures in one AZ.
+- High Availability usually goes hand in hand with horizontal scaling
+
+## High Availability & Scalability for EC2
+
+- Vertical Scaling: Increase instance size (= scale up / down)
+  - From: t2.nano - 0.5G of RAM, 1 vCPU
+  - To: u-12tb1.metal – 12.3 TB of RAM, 448 vCPUs
+- Horizontal Scaling: Increase number of instances (= scale out / in)
+  - Auto Scaling Group
+  - Load Balancer
+- High Availability: Run instances for the same application across multi AZ
+  - Auto Scaling Group multi AZ
+  - Load Balancer multi AZ
+
+## Scalability vs Elasticity (vs Agility)
+
+| **Term**           | **Definition**                                                                                   |
+|--------------------|--------------------------------------------------------------------------------------------------|
+| **Scalability**     | Ability to increase or decrease the capacity to handle varying levels of traffic or load.        |
+| **Elasticity**      | Automatically adjusts resources up or down based on the load in real-time, preventing under or over-provisioning. |
+| **Agility**         | The ability to deploy and manage resources quickly and efficiently in response to changing demands. |
+
+## What is Load Balancing?
+
+- Distributes incoming traffic across multiple targets (EC2 instances, containers, IP addresses) to ensure that no single resource is overwhelmed.
+
+### Why Use a Load Balancer?
+
+- Ensures application fault tolerance and high availability by spreading the load across multiple servers.
+- Protects against failures in a single resource by rerouting traffic automatically.
+- Do regular health checks to your instances
+- Provide SSL termination (HTTPS) for your websites
+
+### Why Use an Elastic Load Balancer?
+
+- **Elastic Load Balancer (ELB)** is a fully managed service that automatically distributes incoming application traffic across multiple targets in one or more Availability Zones.
+- It improves fault tolerance, enhances performance, and scales according to demand.
+- AWS guarantees that it will be working
+- AWS takes care of upgrades, maintenance, high availability
+- AWS provides only a few configuration knobs
+
+#### Types of ELB
+
+1. **Application Load Balancer (ALB)**: For HTTP and HTTPS traffic, operates at Layer 7 (application level).
+2. **Network Load Balancer (NLB)**: Handles high-performance traffic at Layer 4 (transport level).
+3. **Classic Load Balancer**: (slowly retiring) – Layer 4 & 7
+
+## What’s an Auto Scaling Group?
+
+- An **Auto Scaling Group (ASG)** ensures the right number of EC2 instances are running to handle the load.
+- Automatically adjusts the number of instances based on metrics such as CPU utilization or custom-defined thresholds.
+- Can span across multiple AZs to ensure high availability.
+- In real-life, the load on your websites and application can change
+- In the cloud, you can create and get rid of servers very quickly
+- The goal of an Auto Scaling Group (ASG) is to:
+  - Scale out (add EC2 instances) to match an increased load
+  - Scale in (remove EC2 instances) to match a decreased load
+  - Ensure we have a minimum and a maximum number of machines running
+  - Automatically register new instances to a load balancer
+  - Replace unhealthy instances
+- Cost Savings: only run at an optimal capacity (principle of the cloud)
+
+### Auto Scaling Group Scaling Strategies
+
+- **Manual Scaling**: Adjusting the number of instances manually based on load prediction.
+- **Dynamic Scaling**: Automatically adjusts the number of instances based on demand (e.g., CPU usage).
+  - Simple / Step Scaling
+    - When a CloudWatch alarm is triggered (example CPU > 70%), then add 2 units
+    - When a CloudWatch alarm is triggered (example CPU < 30%), then remove 1
+  - Target Tracking Scaling
+    - Example: I want the average ASG CPU to stay at around 40%
+  - Scheduled Scaling
+    - Anticipate a scaling based on known usage patterns
+    - Example: increase the min. capacity to 10 at 5 pm on Fridays
+- **Predictive Scaling**: Uses machine learning to predict future traffic patterns and scales proactively.
+
+## ELB & ASG Summary
+
+- High Availability vs Scalability (vertical and horizontal) vs Elasticity vs Agility in the Cloud
+- Elastic Load Balancers (ELB)
+  - Distribute traffic across backend EC2 instances, can be Multi-AZ
+  - Supports health checks
+  - 3 types: Application LB (HTTP – L7), Network LB (TCP – L4), Classic LB (old)
+- Auto Scaling Groups (ASG)
+  - Implement Elasticity for your application, across multiple AZ
+  - Scale EC2 instances based on the demand on your system, replace unhealthy
+  - Integrated with the ELB