Ref: https://learn.cantrill.io/courses/1820301/lectures/41301338 and https://learn.cantrill.io/courses/1820301/lectures/41301339

• Summary
• Contents:

EC2 Purchase Options = EC2 Launch Types - Overview

• 🔧 Different options & trade-offs when it comes to launching EC2 instances
  • Discounts vs Flexibility: pay less $$$ if you commit in advance or give up flexibility otherwise (e.g. allowing your instances to get interrupted)
  • Pay extra for Reserved Capacity: make sure your instances will be prioritized to be kept alive when EC2 capacity is low
  • Pay extra for Dedicated HW: not sharing HW with other customers comes at a cost
• 💡 Naming:
  • EC2 purchase options → official name
  • EC2 launch types → unofficial name

EC2 Shared Hosts

• 🔧 Shared HW → instances launched in EC2 host that may contain instances from other customers
  • Default
  • Billing: ONLY instance fee, which includes:
    • per-second instance fee (billed for how long instance runs)
    • associated storage capacity fee (billed for how long you keep storage)
  • Diagram (each color indicates instances from different customers)
• Customers have no control over HW
  • Instances of different sizes run on the same EC2 hosts → consumption of a defined allocation of resources
  • Instances from different AWS customers share the same HW
  • Instances still isolated from each other → no interaction with instances from different customers, no awareness of what other stuff is hosted
• On-Demand, Spot and Reserved instances use shared hosts

EC2 On-Demand Instances

• 🔧 Default EC2 Purchase Option, average of everything without specific pros or cons
  • 💡 Choose a different purchase option ONLY when you can justify so

• Characteristics:
  • No interruption
  • No capacity reservation
    • Not prioritized when a lot of AWS HW fails
    • Consider an alternative if instances are business critical
  • Predictable pricing
    • Per-second billing while instance is running (but not when stopped or terminated)
    • Storage consumes capacity if instance is running or stopped → terminate instance if you don't want to get billed for storage (but you can't recover the instance after that)
    • No upfront cost
    • No discounts
    • 💡 Starting price very reasonable (AWS can efficiently allocate resources)
• Best use cases
  • Short-term or unknown workloads
  • Apps which can NOT be interrupted

EC2 Spot Instances

• 🔧 Instances run on spare EC2 capacity (spot capacity) → you bid for spare capacity
  • 👍 Very cheap (up to 90% cheaper than on-demand instances)
  • 👎 Instances will be shut down when spot capacity becomes scarce, i.e. when spot price becomes higher than the max price you were willing to pay
    • ‼️ Apps that use spot instances must tolerate interruptions!!