How to determine the precise reasons why two instance types are incompatible?

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Attempting to change from c4.8xlarge to hpc6a.48xlarge but the option for hpc6a.48xlarge is not available on the "Change instance type" page, implying that the two types are incompatible.

I have gone over the relevant documentation, [https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-resize.html](Compatibility for changing the instance type), but as far as I can tell the two instance types should be compatible.

The AWS console knows something that it is not revealing to the user. How does one determine precisely what the issue is?

Al

AJ
asked 2 years ago358 views
1 Answer
2
Accepted Answer

Make sure the instance type is available in the availability zone:

aws ec2 describe-instance-type-offerings     \
--location-type availability-zone     \
--filters Name=location,Values=us-east-2b Name=instance-type,Values=hpc6a.48xlarge     \
--region us-east-2

For instance in Ohio, it is only available in us-east-2b.

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kentrad
answered 2 years ago
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reviewed 2 years ago
  • @kentrad Should I assume that the availability zones for an instance does not change often and if I want to use that instance type now then I need to move to that region?

  • @kentrad Thanks, save me a lot of time. That page should probably be updated to check the availability zone.

  • An EC2 instance is deployed to a subnet and a subnet is deployed to an availability zone. So, the EC2 instance does not change AZs. To move an instance, you will need to do a snapshot and spin up a new instance in the different subnet/AZ using the snapshot. Or if you are moving to another region, copy the snapshot to the other region and create a new instance in the new region/az/subnet. But check the AZs of your current region to see if that instance type is available.

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