如何从Reserved Instance启动EC2实例？解决计费显示异常问题

Hey there, let's figure out why your EC2 instance is showing up as On-Demand even though you have a matching Reserved Instance (RI). The key point to understand is: you don't actually "launch from" an RI directly—instead, you need to ensure your EC2 instance meets all the critical matching criteria of your RI so AWS automatically applies the RI discount to it. Here's a step-by-step guide to launch an instance that will properly utilize your RI, plus troubleshooting checks to fix your current issue:

First, let's confirm the attributes that must be identical between your RI and EC2 instance:

• Region: If your RI is region-wide, any AZ in that region works; if it's AZ-specific, your instance must be in the exact same AZ.
• Instance Type: Exact match (e.g., t2.micro can't match t2.small).
• Tenancy: Must match (Default, Dedicated, or Dedicated Host).
• Platform: Exact platform category (e.g., Linux/UNIX, Windows Server, SUSE Linux).
• RI State: Your RI must be active (not expired or pending).

Follow these steps to ensure full alignment with your RI:

1. Verify your RI's details first

   • Open the EC2 Console, navigate to the Reserved Instances section in the left sidebar.
   • Locate your active RI and note down all the key attributes listed above (region/AZ, instance type, tenancy, platform).

2. Launch the EC2 instance with matching attributes

   • Go to the EC2 Console and click Launch Instance.
   • Choose an AMI: Select an AMI that matches your RI's platform (e.g., pick an Amazon Linux 2 AMI if your RI is for Linux/UNIX).
   • Choose an Instance Type: Select the exact instance type from your RI (e.g., t3.medium if that's what your RI covers).
   • Configure Instance Details:
     • Network/AZ: If your RI is AZ-specific, select that exact Availability Zone; for region-wide RIs, pick any AZ in the same region.
     • Tenancy: Use the dropdown to select the same tenancy as your RI (Default, Dedicated, or Dedicated Host).
     • Leave other settings (like IAM role, user data) as needed—these don't affect RI matching.
   • Add Storage: Configure storage according to your needs (this doesn't impact RI eligibility).
   • Add Tags: Optional; tags don't affect RI matching.
   • Configure Security Group: Set up your security group as usual.
   • Review and Launch: Double-check all critical attributes (instance type, AZ, tenancy, platform) match your RI, then click Launch and select your key pair to start the instance.

3. Confirm the RI is being utilized

   • Wait 5-10 minutes for AWS's billing system to update.
   • Check the Reserved Instances page: your RI's utilization should show as 100% (if it's a single-instance RI).
   • You can also verify in the Billing Console's Cost Explorer—filter for the instance and check that its usage is categorized under Reserved Instance.

If you've followed the steps and it's still On-Demand, check these:

• Ensure your RI hasn't expired: Go to Reserved Instances and confirm the end date is in the future.
• Check tenancy again: If your RI is Dedicated, your instance can't be set to Default tenancy.
• Platform mismatch: Some RIs are for specific platforms (e.g., Windows Server 2019 vs. general Windows)—confirm your AMI matches the RI's platform exactly.
• Instance state: Stopped instances don't consume RI capacity; your instance must be in the Running state.

内容的提问来源于stack exchange，提问作者Eleena jose