Logical Enigma
AWS Notes

High Availability

Elastic Load Balancers

  • InService / OutofService -
  • Can spread across AZs, not regions
  • Application Load Balancer
    • HTTP/HTTPS - Layer 7. Application aware
    • Advanced request routing, route requests to specific web servers
    • Target Groups to specify EC2, etc.
    • Allows Rules on many different variables
  • Network Load Balancer
    • TCP traffic where extreme performance required - Layer 4
    • Millions of requests per second while maintaining ultra-low latencies
  • Classic load balancer
    • Legacy - Layer 7-specific features, but not application aware
    • Can use X-Forwarded-For (the user IP address, otherwise your application will see the load balancer IP) and sticky
    • Can use strict Layer 4
    • Responds with 504 Gateway time-out if having issues - web or db server?
  • Sticky Sessions - bind a user’s session to a particular EC2 instance
    • Classic load balancer -> target particular ec2
    • Application Load Balancer -> target group level
  • Cross Zone Load Balancing - When enabled ELB can send to multiple AZs
  • Path Patterns - path-based routing
  • Auto Scaling
    • Groups - logical groups e.g. Web Server, DB Servers
    • Configuration Templates (launch template or launch configuration)
    • Scaling Options - several options - dynamic scaling or schedule
    • Maintain current instance levels at all times - periodic health check
    • Scale manually - specify maximum, minimum, desired capacity
    • Scale based on schedule - best for predictable schedule
    • Scale based on demand - scaling policies - define parameters that control the scaling process. CPU ~ 50 percent, etc
    • Use predictive scaling - use EC2 Auto Scaling with AWS Auto Scaling
    • Create Launch Configuration and then an AutoScaling Group (moving to Launch Templates)
  • CloudFormation - script your cloud environment. Quick Starts allow you use stacks created by AWS Architects
  • Elastic Beanstalk - aimed at developers that don’t want to learn cloud formation. ASG and growing.
  • Bastion Hosts Highly Available:
    • 2 EC2 Instances, 2 Availability Zones, Network Load Balancer w/ static IP (layer 4 b/c port 22)
    • 1 EC2 Instance + EIP, Auto Scaling group w/ 2 Availability Zones - UserData script to take over that EIP
  • On-Premises Services with AWS
    • Database Migration Service (DMS)
    • Allows you to move databases to and from AWS
    • Might have DR in AWS and primary is on-prem
    • Works w/ most popular DB: oracle, mysql, dynamodb
    • Homogenous & heterogeneous migrations
    • Server Migration Service (SMS)
    • Incremental replication of your on-prem servers into AWS
    • Can be used as a backup tool, multi-site strategy (on-prem, off-prep), DR tool
    • AWS Application Discovery Service
    • Helps enterprise customers plan migration projects by gathering information from their on-premises data centers
    • Agentless connect installs as virtual appliance in VMware vCenter
    • Build utilization map and dependency map
    • Encrypted data up to AWS, estimate Total Cost of Ownership and plan
    • Also available in the AWS Migration Hub where you can migrate discovered servers and track their progress as they get to AWS
    • VM Import/Export - migrate existing to EC2, DR tool, allow you to export AWS Ec2 to VM
    • Download Amazon Linux 2 as an ISO - VMware, Hyper-V, Kvm, VirtualBox

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