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Vivesh
Vivesh

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Cloud Migration Strategies

#cloud #migration #devops #discuss

Introduction to Cloud Migration

_Cloud migration is the process of moving applications, data, and workloads from an on-premise environment to the cloud. A well-planned migration ensures minimal disruption, maximized performance, and optimized costs.

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Common Cloud Migration Strategies (6 R's)

  1. Rehosting ("Lift and Shift"):

    • Directly moving applications to the cloud without significant changes.
    • Best for legacy systems with minimal modification needs.

  2. Replatforming ("Lift, Tinker, and Shift"):

    • Making minor optimizations to leverage cloud benefits without major architecture changes.
    • Example: Switching databases to a cloud-managed version.

  3. Repurchasing:

    • Replacing the existing application with a cloud-native SaaS solution.
    • Example: Moving from a self-hosted CRM to Salesforce.

  4. Refactoring/Re-architecting:

    • Redesigning applications to take full advantage of cloud-native features (e.g., serverless computing, microservices).
    • Best for modernizing applications for scalability and performance.

  5. Retiring:

    • Decommissioning outdated or unnecessary systems instead of migrating them.

  6. Retaining:

    • Keeping certain applications on-premise for compliance or technical reasons.

Cloud Migration Plan for an On-Premise Application

1. Assess Current Environment

  • Inventory existing infrastructure, applications, and dependencies.
  • Evaluate application performance, scalability, and resource requirements.
  • Identify applications and data suitable for migration.

2. Define Migration Goals

  • Key Objectives:
    • Improve scalability and performance.
    • Reduce infrastructure maintenance costs.
    • Increase availability and disaster recovery capabilities.
    • Enhance security and compliance.

3. Choose a Cloud Provider

  • AWS, Azure, or Google Cloud Platform based on:
    • Budget.
    • Specific features (e.g., serverless, managed services).
    • Compliance requirements (e.g., GDPR, HIPAA).

4. Select a Migration Strategy

  • For this plan, we'll use a Replatforming strategy:
    • Move the on-premise application to a cloud VM (e.g., AWS EC2).
    • Transition the database to a managed service (e.g., Amazon RDS).

5. Migration Plan Steps

Step 1: Pre-Migration Preparation

  • Analyze application dependencies and identify services to move.
  • Create a migration timeline to minimize downtime.
  • Back up all application data to ensure data safety.

Step 2: Set Up the Cloud Environment

  • Provision Resources:
    • Create a Virtual Private Cloud (VPC) with public and private subnets.
    • Launch EC2 instances for the application.
    • Configure a load balancer for high availability.
  • Database Migration:
    • Set up Amazon RDS for the database.
    • Use AWS Database Migration Service (DMS) to migrate data from on-premise to RDS.

Step 3: Configure Networking and Security

  • Set up security groups and firewalls to restrict access.
  • Use IAM roles and policies to manage permissions.
  • Configure a VPN or Direct Connect for secure communication between on-premise and cloud environments during migration.

Step 4: Data Migration

  • Migrate static files to Amazon S3.
  • Use AWS Snowball for large datasets or AWS DataSync for continuous file synchronization.

Step 5: Application Migration

  • Package the application into containers (if applicable) for easy deployment.
  • Use AWS Elastic Beanstalk or Kubernetes for deployment orchestration.
  • Test the application in the cloud environment.

Step 6: Testing and Optimization

  • Test application performance, latency, and functionality.
  • Optimize instance types, storage, and autoscaling policies to reduce costs.

Step 7: Cutover and Go Live

  • Schedule a maintenance window for the final cutover.
  • Redirect DNS (using Amazon Route 53) to point traffic to the cloud-hosted application.

Step 8: Post-Migration Review

  • Monitor the application using Amazon CloudWatch or another monitoring tool.
  • Address any performance issues or bottlenecks.
  • Optimize resources to ensure cost efficiency.

Example AWS Architecture for the Migrated Application

  1. Compute:

    • EC2 instances in an Auto Scaling group.

  2. Database:

    • Amazon RDS with Multi-AZ deployment for high availability.

  3. Storage:

    • Amazon S3 for static content and backups.

  4. Networking:

    • VPC with public and private subnets.
    • Elastic Load Balancer for distributing traffic.

  5. Monitoring:

    • Amazon CloudWatch for metrics and alerts.

Terraform Configuration

1. Providers and Variables 

provider "aws" { region = "us-east-1" # Change as needed } variable "vpc_cidr" { default = "10.0.0.0/16" } variable "public_subnets" { default = ["10.0.1.0/24", "10.0.2.0/24"] } variable "private_subnets" { default = ["10.0.3.0/24", "10.0.4.0/24"] } variable "db_username" { default = "admin" # Set your username } variable "db_password" { default = "yourpassword" # Use secrets management for production } variable "instance_type" { default = "t3.micro" # Modify as needed }
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2. Networking: VPC, Subnets, Internet Gateway, and Security Groups 

resource "aws_vpc" "main" { cidr_block = var.vpc_cidr } resource "aws_subnet" "public" { count = length(var.public_subnets) vpc_id = aws_vpc.main.id cidr_block = var.public_subnets[count.index] map_public_ip_on_launch = true } resource "aws_subnet" "private" { count = length(var.private_subnets) vpc_id = aws_vpc.main.id cidr_block = var.private_subnets[count.index] } resource "aws_internet_gateway" "igw" { vpc_id = aws_vpc.main.id } resource "aws_route_table" "public_rt" { vpc_id = aws_vpc.main.id } resource "aws_route" "default_route" { route_table_id = aws_route_table.public_rt.id destination_cidr_block = "0.0.0.0/0" gateway_id = aws_internet_gateway.igw.id } resource "aws_security_group" "web_sg" { vpc_id = aws_vpc.main.id ingress { from_port = 80 to_port = 80 protocol = "tcp" cidr_blocks = ["0.0.0.0/0"] } ingress { from_port = 443 to_port = 443 protocol = "tcp" cidr_blocks = ["0.0.0.0/0"] } egress { from_port = 0 to_port = 0 protocol = "-1" cidr_blocks = ["0.0.0.0/0"] } } resource "aws_security_group" "db_sg" { vpc_id = aws_vpc.main.id ingress { from_port = 3306 to_port = 3306 protocol = "tcp" security_groups = [aws_security_group.web_sg.id] } egress { from_port = 0 to_port = 0 protocol = "-1" cidr_blocks = ["0.0.0.0/0"] } }
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3. Compute: EC2 Instances with Auto Scaling 

resource "aws_launch_configuration" "app" { name = "app-launch-configuration" image_id = "ami-0c02fb55956c7d316" # Amazon Linux 2 instance_type = var.instance_type security_groups = [aws_security_group.web_sg.id] lifecycle { create_before_destroy = true } } resource "aws_autoscaling_group" "app_asg" { desired_capacity = 2 max_size = 3 min_size = 1 launch_configuration = aws_launch_configuration.app.id vpc_zone_identifier = aws_subnet.public[*].id tag { key = "Name" value = "app-instance" propagate_at_launch = true } }
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4. Database: RDS Instance 

resource "aws_db_subnet_group" "db" { name = "db-subnet-group" subnet_ids = aws_subnet.private[*].id } resource "aws_db_instance" "app_db" { allocated_storage = 20 engine = "mysql" instance_class = "db.t3.micro" name = "appdb" username = var.db_username password = var.db_password vpc_security_group_ids = [aws_security_group.db_sg.id] db_subnet_group_name = aws_db_subnet_group.db.name multi_az = true skip_final_snapshot = true }
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5. Storage: S3 Bucket for Static Files 

resource "aws_s3_bucket" "static" { bucket = "app-static-files-${random_id.bucket_id.hex}" acl = "public-read" tags = { Name = "StaticFilesBucket" } } resource "random_id" "bucket_id" { byte_length = 8 }
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6. Load Balancer 

resource "aws_lb" "app_lb" { name = "app-load-balancer" internal = false load_balancer_type = "application" security_groups = [aws_security_group.web_sg.id] subnets = aws_subnet.public[*].id } resource "aws_lb_target_group" "app_tg" { name = "app-target-group" port = 80 protocol = "HTTP" vpc_id = aws_vpc.main.id } resource "aws_lb_listener" "http_listener" { load_balancer_arn = aws_lb.app_lb.arn port = 80 protocol = "HTTP" default_action { type = "forward" target_group_arn = aws_lb_target_group.app_tg.arn } } resource "aws_autoscaling_attachment" "asg_attachment" { autoscaling_group_name = aws_autoscaling_group.app_asg.name target_group_arn = aws_lb_target_group.app_tg.arn }
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How to Deploy This Configuration

  1. Install Terraform on your local machine.
  2. Save the configuration in a .tf file (e.g., main.tf).
  3. Initialize Terraform: 
 terraform init
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  1. Validate the configuration: 
 terraform validate
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  1. Plan the deployment: 
 terraform plan
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  1. Deploy the resources: 
 terraform apply
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Summary

Migrating an on-premise application to the cloud requires careful planning, execution, and testing. By following a structured migration strategy like the one outlined above, organizations can achieve improved scalability, reliability, and cost savings while minimizing downtime and risks.

Happy Learning !!!

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