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EC2 Instance Purchasing Options

Links: 101 AWS SAA Index

On Demand Instances

  • Short uninterrupted workload.
  • More expensive than spot and reserved.

Capacity Reservations

  • Reserve capacity in a specific AZ for any duration.
    • If you want to make reservations in multiple AZs then you need to file multiple reservation requests.
  • We can do a capacity reservation of on demand instances.
  • There is no time commitment (like 1 or 3 years) and no monetary benefit but there is a guarantee that you will have capacity when you need it.
    • This is particularly useful when you know that you will be needing an instances for an uninterrupted workload at a particular time.
  • The main benefit of capacity reservation over reserved instances is there is no need of 1 or 3 years of commitment.
  • For monetary benefit you can use capacity reservation with savings plan.
  • They can't be used with dedicated hosts or placement groups.
You're charged at On-Demand rate whether you run instances or not.
We can do a capacity reservation in zonal reserved instances but NOT in regional reserved instances.

Reserved Instances

  • Reserved Instances are not physical instances, but rather a billing discount applied to the use of On Demand Instances in your account.

Standard Reserved

  • 72% cheaper than on demand.
  • For stable applications like database.
  • Commitment of 1 (minimum) or 3 years.
    • For 3 years you get more discounts.
  • Payment options are no upfront (no discount), partial upfront (discount +) and full upfront (discount +++)
  • We reserve a specific instance type.
  • Reserved Instance’s Scope – Regional or Zonal (reserve capacity in an AZ)
  • Unused Standard Reserved Instances can later be sold at the Reserved Instance Marketplace.

Convertible Reserved

  • We can change the instance type.
  • Less cost savings as compared to normal reserved.
Convertible unused instances cannot be sold in the Reserved instance marketplace.

EC2 Savings Plan

  • Get a discount based on long-term usage (up to 72% - same as Reserver instances)
  • Commit to a certain type of usage ($10/hour for 1 or 3 years)
  • Usage beyond EC2 Savings Plans is billed at the On-Demand price.
  • Locked to a specific instance family & AWS region (e.g., M5 in us-east-1)
  • Flexible across:
    • Instance Size (e.g., m5.xlarge, m5.2xlarge)
    • OS (e.g., Linux, Windows)
    • Tenancy (Host, Dedicated, Default)

Spot

  • Highest discount 90% as compared to on demand.
  • Can lose them at any moment.
  • Suitable for batch jobs, data analysis etc.
  • We get a spot instance if current spot price < max spot price defined by us.
  • If current spot price is greater then instance has to be stopped or terminated. We have a grace period of 2 minutes.
  • Spot pricing can vary depending on AZ.

Dedicated Hosts

  • For compliance reasons and server bound software licenses (complex licensing, BYOL - Bring your own license).
  • Purchasing options:
    • On-demand - pay per second for active Dedicated Host
    • Reserved - 1 or 3 years (No Upfront, Partial Upfront, All Upfront)
  • Most expensive option.
  • With dedicated hosts you have additional control and visibility on how instances are placed on the server.
  • With Dedicated Host the physical server is basically yours. It does not change, it's always the same physical machine for as long as you are paying.
Keywords:
  • Compliance,
  • software license (BYOL),
  • 3 year,
  • same physical machine,
  • visibility and control.
  • Socket level configurations.

Dedicated Instances

  • Instances running on hardware dedicated to you.
  • Dedicated instances may share hardware with other instances from the same AWS account that are not dedicated instances.
  • Dedicated instances CANNOT be used for existing server-bound software licenses.
  • Billing per instance.
  • Automatic instance placement.
  • Your instance runs on some dedicated hardware. Its not lockdown to you. If you stop/start instance, you can get some other hardware somewhere else. Basically, the hardware is "yours" (you are not sharing it with others) for the time your instance is running. You stop/start it, you may get different physical machine later on (maybe older, maybe newer, maybe its specs will be a bit different), and so on. So your instance is moved around on different physical servers - whichever is not occupied by others at the time.
  • If you see keyword single tenancy in questions then go for dedicated instances.

??? important]+ Dedicated hosts also offers single tenancy but it is MORE expensive. [DVA - 1 "Dedicated hosts also offers single tenancy but it is MORE expensive. [DVA - 1]" - So unless there is a demand for licensing go for dedicated instances. - In short dedicated instances are the most cost effective way of achieving single tenancy.

Keywords:
  • Single tenancy
  • Cheaper than dedicated hosts

Summary

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Last updated: 2023-03-24