Question about Shared Tenancy and OS release in light of EC2 Instance Savings Plan

Question

Hi re:Post,
Thank you for your time and help with my questions.

1) Tenancy: EC2 - our servers all have the 'default' tenancy, which means their tenancy is shared.
Does this mean that an AWS host server can have other instances from multiple customers in addition to our our own instances?

2) OS:  We're looking at EC2 Instance Savings Plan and have been reading:

https://docs.aws.amazon.com/pdfs/savingsplans/latest/userguide/savingsplans.pdf

Regarding, page 6:  and "Regardless of .... OS"

```
EC2 Instance Savings Plans provide savings up to 72 percent off On-Demand, in exchange
for a commitment to a specific instance family in a chosen AWS Region (for example, M5 in
Virginia). These plans automatically apply to usage regardless of size (for example, m5.xlarge,
m5.2xlarge, etc.), OS (for example, Windows, Linux, etc.), and tenancy (Host, Dedicated,
Default) within the specified family in a Region.
```
Does the "Regardless" include different releases within the Linux OS family?
We have all Linux OS but may have different releases of Linux.
Would that scenario be okay with an EC2 Instance Savings Plan?

Thank you for your time and help!

Best Regards,

Donald

re:Post Agent · Accepted Answer

Thank you for your questions about EC2 Instance Savings Plans and tenancy. I'll address each of your points:

1. Regarding shared tenancy:
Yes, when you use the 'default' tenancy (also known as shared tenancy), your EC2 instances may indeed run on AWS host servers that also host instances from other AWS customers. This is the standard multi-tenant model that allows AWS to efficiently utilize their hardware resources. However, AWS has robust isolation mechanisms in place to ensure security and performance isolation between different customers' instances.

2. Regarding OS considerations for EC2 Instance Savings Plans:
You're correct in your understanding of the EC2 Instance Savings Plans. The "regardless of OS" clause does include different releases within the Linux OS family. This means that your EC2 Instance Savings Plan will apply to your usage regardless of which specific Linux distribution or version you're running on your instances.

So, in your scenario where you have all Linux OS but potentially different releases of Linux, this would be perfectly fine with an EC2 Instance Savings Plan. The plan will apply to your usage as long as you're using the specified instance family in the chosen AWS Region, regardless of the specific Linux release.

This flexibility allows you to update or change your Linux distributions as needed without affecting the application of your Savings Plan. Whether you're running Amazon Linux, Ubuntu, CentOS, or any other Linux distribution, and regardless of the version, your EC2 Instance Savings Plan will still apply, providing you with the committed discount.

Remember that EC2 Instance Savings Plans are specific to an instance family in a particular region. So as long as you're using the instance family you committed to (e.g., M5) in the specified region, you'll receive the discounted rate regardless of the Linux release you're running.  
**Sources**  
[Amazon EC2 FAQs – AWS](https://aws.amazon.com/ec2/faqs/)  
[Compute Savings Plans and Reserved Instances - Savings Plans](https://docs.aws.amazon.com/savingsplans/latest/userguide/sp-ris.html)  
[Savings Plans - Amazon EC2 Reserved Instances and Other AWS Reservation Models](https://docs.aws.amazon.com/whitepapers/latest/cost-optimization-reservation-models/savings-plans.html)

Question about Shared Tenancy and OS release in light of EC2 Instance Savings Plan

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