Elastic Compute Cloud (EC2)

• Pricing models
  • On-Demand: fixed-rate by hour or second, no commitments
  • Spot: bid on spare compute for up to 90% off On-Demand prices, can be interrupted
  • Reserved: capacity reservation for one to three year term providing up to 75% off On-Demand prices
  • Dedicated Hosts: physical server dedicated to you, useful for server-bound licenses, purchased On-Demand or Reserved
  • Comparision site
• Instance Store volumes are ephemeral, they can be restarted, but cannot be stopped, will lose data if the underlying host fails, and cannot be kept after termination. Prefer EBS.
• Security Groups
  • By default, all inbound traffic is blocked and all outbound traffic is allowed
  • They are stateful, if you send a request from your instance, response traffic for request is allowed regardless of inbound rules. Similarly, responses to allowed inbound traffic are allowed to flow out, regardless of outbound rules.
  • Only support allow rules, not deny
• Instance metadata available at http://169.254.169.254/latest/meta-data/ and user data at http://169.254.169.254/latest/user-data/
• Placement Groups
  • Clustered: low latency and high throughput networking, each is in close proximity in the same AZ
  • Spread: individual critical instances, each is on separate racks and can be multi-AZ
  • Partitioned: large distributed and replicated workloads with multiple instances, each partition is on separate racks and can be multi-AZ
• Networking
  • Elastic Network Interface (ENI) for basic networking
  • Enhanced Network Adapter (ENA) for speeds between 10 and 100 Gbps
  • Elastic Fabric Adapter (EFA) for high-performance computing (HPC), machine learning (ML), or OS bypass

Elastic Block Store (EBS)

• By default, root volumes are deleted when the instance is terminated but additional volumes are not
• Always in the same availability zone (AZ) as the running instance
• Volume Types
  • SSD
    • General Purpose (gp2), balances price and performance, max 16,000 IOPS
    • Provisioned IOPS (io1), high performance designed for databases
  • HDD
    • Throughput Optimized (st1), frequently accessed big data, data warehouses, and log processing
    • Cold (sc1), lowest cost for less frequency accessed data
• Snapshots
  • Preferably taken on stopped instances, but not required
  • Stored on S3 and incremental, only blocks changed since last snapshot are saved
  • Automatically encrypted if volume is encrypted
  • Can only share snapshots with other accounts or make public if unencrypted
• To move a volume from one AZ or Region to another
  1. Create a snapshot
  2. If unencrypted, optionally copy snapshot as encrypted
  3. Create an AMI from the snapshot
  4. If moving to a new region, copy AMI to desired region
  5. Use the AMI to launch an instance in desired AZ

Elastic Load Balancer (ELB)

• Use to distribute traffic across multiple targets in a single and across multiple AZs (if enabled)
• To use in a VPC, need a minimum of two public subnets
• 504 means there’s likely an issue with your application
• Instance health checks are shown as either InService or OutOfService
• Get client IP using X-Forwarded-For header
• Types
  • Application Load Balancer (ALB)
    • Layer 7, allowing for things like path-based traffic routing
    • Preferred for most applications
    • Given DNS name, not IP
  • Network Load Balancer (NLB)
    • Layer 4
    • High performance
    • Can assign a static IP
  • Classic Load Balancer
    • Lower cost, legacy solution
    • Given DNS name, not IP