I am seeing a strange behavior where on a preview it wants to replace the entire ec2 instance because it thinks ebsBlockDevices parameters/objects have changed.. however, it wants to change it to the same name.. AKA, nothing has actually changed, which is correct

can you share your code?

Jamie was helping me out with this issue. I created this simplified example to help troubleshoot the issue: If I create an AMI from an instance with multiple volumes, and launch an instance from that AMI - if I later try to resize the additional volume on the new instance, Pulumi doesn't resize the volume. Instead it wants to replace the entire instance.

"""Testing Multi-Volume AMIs and Post-Deploy Volume Resizing"""

import pulumi
import pulumi_aws as aws

ubuntu_ami = aws.ec2.get_ami(most_recent=True,
    filters=[
        aws.ec2.GetAmiFilterArgs(
            name="name",
            values=["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"],
        ),
        aws.ec2.GetAmiFilterArgs(
            name="virtualization-type",
            values=["hvm"],
        ),
    ],
    owners=["099720109477"])

# Create an instance with an addditional volume
test_ami_origin = aws.ec2.Instance(
    "test_ami_origin",
    ami=ubuntu_ami.id,
    instance_type="t3.micro",
    tags={"Name": "test_ami_origin",},
    ebs_block_devices=[
        aws.ec2.InstanceEbsBlockDeviceArgs(
            device_name="/dev/sdc",
            volume_size=200,
            volume_type="gp2",
        )
    ],
    subnet_id="subnet-014a297abc46f0170"
    )

# Create an AMI from that instance
prod_ppgdb_ami = aws.ec2.AmiFromInstance(
    "prod_ppgdb_ami",
    source_instance_id=test_ami_origin.id,
)

# First, create a new instance from that AMI,
# Then, uncomment the ebs_block_devices attribute and `pulumi up` again.
# This will trigger replacement of the entire instance, instead of resizing the drive.
test_instance_from_ami = aws.ec2.Instance(
    "test_instance_from_ami",
    ami=prod_ppgdb_ami.id,
    instance_type="t3.micro",
    subnet_id="subnet-014a297abc46f0170",
    # ebs_block_devices=[
    #     aws.ec2.InstanceEbsBlockDeviceArgs(
    #         device_name="/dev/sdc",
    #         volume_size=250,
    #         volume_type="gp2",
    #     )]
    )

@billowy-army-68599 sorry, just seeing this, JC posted the code in the channel

I cross posted this to #general since it doesn't seem python-specific

Changes to volume size trigger a replacement. https://www.pulumi.com/registry/packages/aws/api-docs/ec2/instance/#instanceebsblockdevice