Unable to preserve iops when migrating EBS volume from io1 to gp3

[jonnydh]

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Terraform CLI and Terraform AWS Provider Version

Terraform v1.0.4
on darwin_amd64
+ provider registry.terraform.io/hashicorp/aws v3.53.0

Affected Resource(s)

• aws_ebs_volume

Terraform Configuration Files

Pre-migration (legacy code)

resource "aws_ebs_volume" "upgrade_preserved_iops" {
  availability_zone = "eu-west-2a"
  size              = 100
  iops              = 4000
  type              = "io1"

  tags = {
    Name = "upgrade_preserved_iops"
  }
}

resource "aws_ebs_volume" "upgrade_changed_iops" {
  availability_zone = "eu-west-2a"
  size              = 100
  iops              = 4000
  type              = "io1"

  tags = {
    Name = "upgrade_changed_iops"
  }
}

Migration code

resource "aws_ebs_volume" "upgrade_preserved_iops" {
  availability_zone = "eu-west-2a"
  size              = 100
  iops              = 4000
  type              = "gp3"

  tags = {
    Name = "upgrade_preserved_iops"
  }
}

resource "aws_ebs_volume" "upgrade_changed_iops" {
  availability_zone = "eu-west-2a"
  size              = 100
  iops              = 4001
  type              = "gp3"

  tags = {
    Name = "upgrade_changed_iops"
  }
}

Expected Behavior

When migrating an existing EBS io1 volume to gp3, the iops value should be preserved.

Actual Behavior

When migrating to gp3, and attempting to preserve the existing iops value, the iops value is instead set to the gp3 default of 3000.

Further Info:

If we have an existing EBS io1 volume with (for example) 4000 iops set. Attempting to change the volume_type from io1 to gp3 (but preserving desired iops at 4000) in terraform will result in the iops defaulting to 3000 (the gp3 default).

This causes further frustration, as it cannot be quickly resolved with another terraform apply - as there is a modification limit preventing further changes for another 6 hours.

However, if we perform the migration with the desired iops changed to 4001, the terraform apply works as expected.

Impact:

This significantly slowed down our migration from io1 to gp3, and required greater manual effort.

Steps to Reproduce

1. Create config for io1 EBS volumes with 4000 iops, as per the Terraform Configuration Files -pre migration (legacy code) section above.
2. Run terraform apply
3. Checking in AWS console shows two EBS volumes with 4000 iops each.
4. Modify the config per the Terraform Configuration Files - migration code section above.
5. Run terraform apply
6. Checking in AWS console shows the upgrade_preserved_iops volume incorrectly set to 3000 iops. The upgrade_changed_iops volume is correctly set to 4001 iops.

[leonardobiffi]

Hi, I submit a suggestion to fix this problem #23280

[github-actions]

This functionality has been released in v4.17.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.