AWS Certified Cloud Practitioner CLF-C01 Elastic Load Balancing

Scalability & High Availability

Scalability : ability to accomodate a larger load by making the hardware stronger (scale up), or by adding nodes (scale out).
Vertical Scalability : increasing the size of the instance
(t2.micro->t2.large)
Horizontal Scalability : increasing the number of instances / systems for your application

The goal of high availability is to survive a data center loss.(availability zones)

Elasticity

once a system is scalable, elasticity means that there will be some 'auto-scaling' so that the system can scale based on the load. This is 'cloud-friendly': pay-per-use, match demand, optimize costs

Agility

new IT resources are only a click away, which means that you reduce the time to make those resources avilable to your developers from weeks to just minutes.

Elastic Load Balancer

is a managed load balancer which AWS guarantees that it will be working.

• Application Load Balancer(HTTP/HTTPS only) -Layer 7
• Network Load Balancer(ultra-high performance, allows for TCP) -Layer 4
• Classic Load Balancer (slowly retiring)

Auto Scaling Group

create and get rid of servers very quickly. Automatically register new instances to a load balancer. Replace unhealthy instances. only run at an optimal capacity (Cost savings).

Scaling Strategies

• simple/step scaling : CloudWatch alarm이 울리면 (예를들어 CPU >70%) 유닛 2개 증가하기
• track tracking scaling : average ASG CPU가 40% 미만이 되도록 설정등과 같이 tracking하며 유지되게 만듦
• scheduled scaling : usage patterns에 따라 auto scaling.