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All technological notes.

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AWS - Global Infrastructure

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• AWS - Global Infrastructure
  • Terminologies
  • High Availability
    • Elastic Load Balancer (ELB)
  • High Scalability
  • High Elasticity
    • Auto Scaling Groups (ASG)
  • Hight Agility
  • Highly Fault Tolerant
  • High Durability
    • Business Continuity Plan
  • Summary
  • Architectural Diagram Example

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Terminologies

• Solution Architect:

  • A role in a technical organization that architects a technical solution using multiple systems via researching, documentation, experimentation.

• Cloud Architect

  • A solution architect that is focused solely on architecting technical solution using cloud services.
  • needs to understand the following terms and factor them into their designed architecture based on the business requirement.
    • Availability: The ability to ensure a service remains available. e.g. Highly Available(HA)
    • Scalability: The ability to grow rapidly or unimpeded.
    • Elasticity: The abilibty to shrink and grow to meet the demand.
    • Fault Tolerance: The ability to prevent a failure.
    • Disaster Recovery: The ability to recover from a failure. e.g.Highly Durable(DR)
    • Security: How secure is this solution?
    • Cost: How much is this going to cose.

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High Availability

• The ability for the service to remain available by ensuring there is no single point of failure and/or ensure a certain level of performance.

• High Availability usually goes hand in hand with horizontal scaling

• High availability means running your application / system in at least 2 Availability Zones

• The goal of high availability is to survive a data center loss (disaster)

• Services:

  • Auto Scaling Group multi AZ
  • Load Balancer multi AZ

• Example: Multiple Availability Zones

• Use Case: Beanstalk

• Use Case: RDS

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Elastic Load Balancer (ELB)

• Load Balancing

  • servers that forward internet traffic to multiple servers (EC2 Instances) downstream.

  • Advantages

    • Spread load across multiple downstream instances
    • Expose a single point of access (DNS) to your application
    • Seamlessly handle failures of downstream instances
    • Do regular health checks to your instances
    • Provide SSL termination (HTTPS) for your websites
    • High availability across zones

• Elastic Load Balancer (ELB)

  • A load balancer allows to evenly distribute traffic to multiple servers in one or more datacenter.
    • If a datacenter or server becomes unavailable (unhealthy) the load balancer will route the traffic to only available dataceners with servers.
• AWS guarantees that it will be working
• AWS takes care of upgrades, maintenance, high availability
• AWS provides only a few configuration knobs
• It costs less to setup your own load balancer but it will be a lot more effort on your end (maintenance, integrations)
• 4 kinds of load balancers offered by AWS:
  • Application Load Balancer (HTTP / HTTPS only) – Layer 7
  • Network Load Balancer (ultra-high performance, allows for TCP) – Layer 4
  • Gateway Load Balancer – Layer 3
  • Classic Load Balancer (retired in 2023) – Layer 4 & 7

Application Load Balancer	Network Load Balancer	Gateway Load Balancer
HTTP / HTTPS / gRPC protocols	TCP / UDP protocols	GENEVE Protocol on IP Packets
Application Layer 7	Transport Layer 4	Network Layer 3
HTTP Routing features	High Performance: millions of request per seconds	Route Traffic to Firewalls that you manage on EC2 Instances
Static DNS (URL)	Static IP through Elastic IP	ntrusion detection

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High Scalability

• The ablity to increase the capacity based on the increasing demand of traffic, memory and computing power.

• ability to accommodate a larger load by making the hardware stronger (scale up), or by adding nodes (scale out)

• 2 Kinds of Scalability:

  • Vertical Scaling:

    • Scaling Up / Down
    • increasing/decreasing the size of the instance
    • eg.
      • Upgrade to a bigger server.
      • t2.micro -> t2.large
    • very common for non distributed systems, such as increasing the size of a database.
    • There’s usually a limit to how much you can vertically scale (hardware limit)

  • Horizonal Scaling: elasticity

    • Scaling Out / In:
    • increasing/decreasing the number of instances / systems for your application
    • Add more servers of the same size.
    • implies distributed systems
    • very common for web applications / modern applications
    • Services:
      • Auto Scaling Group
      • Load Balancer

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High Elasticity

• The ability to automatically increase or decrease the capacity based on the current demand of traffic, memory and computing power.

• “auto-scaling” so that the system can scale based on the load.

  • This is “cloud-friendly”: pay-per-use, match demand, optimize costs

• Horizonal Scaling

  • Scaling Out: Add more servers of the same size.
  • Scaling In: Removing underutilized servers of the same size.

• Vertical Scaling is generally hard for traditional architecture so user will usually only see horizontal scaling described with Elasticity.

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Auto Scaling Groups (ASG)

• Auto Scaling Groups (ASG)

  • an AWS feature that will automatically add or remove servers based on scaling rules user define based on metrics.
  • 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)

• Scaling Strategies

  • Manual Scaling:
    • Update the size of an ASG manually
  • Dynamic Scaling: Respond to changing demand
    • 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 ahead of time
      • Automatically provisions the right number of EC2 instances in advance
      • Useful when your load has predictable time based patterns

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Hight Agility

• Agility: (not related to scalability - distractor)
  • new IT resources are only a click away, which means that you reduce the time to make those resources available to your developers from weeks to just minutes. 缩短时间

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Highly Fault Tolerant

• The ability for the service to ensure there is no single point of failure, preventing the chance of failure.

• Fail-overs

  • When user have a plan to shift traffic to a redundant system in case the primary system fails.

• Example: RDS Multi-AZ

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High Durability

• The ability to recover from a disaster and to prevent the loss of data.

• Disaster Revocery (DR)

  • the solution that recover from a disaster.
  • factors to be considered:
    • Do you have a backup?
    • How fast can you restore that backup?
    • Does your backup still work?
    • How do you ensure current live data is not corrupt?

• CloudEndure Disaster Recovery

  • continuously replicates user’s machines into a low-cost staging area in user’s target AWS account and preferred Region enabling fast and reliable recovery in case of IT data center failures.

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Business Continuity Plan

• Business Continuity Plan (BCP)

  • a document that outlines how a business will continue operating during an unplanned distruption in services.

  

• Disaster Recovery Option

  • Backup & Restore: backup data and restore them to new infrastructure.

    • Lower priority use cases
    • Restore Data after event
    • Deploy resources after event
    • Cost: $

  • Pilot Light: data is replicated to another region with the minimal services running

    • Less stringent RTO & ROP
    • Core Services
    • Start and scale resources after event
    • Cost: $$

  • Warm Standby: scaled down copy of user’s infrastructure running ready to scale up.

    • Business Critical Services
    • Scale resources after event
    • Cost: $$$

  • Multi-site: Scaled up copy of user’s infrastructure in another region.

    • Zero downtime
    • Nero zero loss
    • Mission Critical Services
    • Cost: \(\)

  

• Recoery Time Objective (RTO)

  • the maximum acceptable delay between the interruption of service and restoration of service.
  • This objective determines what is considered an acceptable time window when service is unavailble and is defined by the organization.

  

• Recoery Point Objective (RPO)

  • the maximum acceptable amount of data since the last data recovery point.
  • This objective determines what is considered an acceptable loss of data between the last recovery point and interruption of service and is defined by the organization.

  

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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
  • 4 types:
    • Classic (old),
    • Application (HTTP – L7),
    • Network (TCP – L4),
    • Gateway (L3)
• 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

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Architectural Diagram Example

• AWS Architecture Icons: https://aws.amazon.com/architecture/icons/

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