Set the automatic_backup_retention_days attribute in aws_fsx_lustre_file_system resource to a nonzero value.

Example Configuration

data "aws_vpc" "selected" {
  filter {
    name   = "tag:Name"
    values = ["aws-controltower-VPC"]
  }
}

data "aws_subnet" "selected-1" {
  filter {
    name   = "tag:Name"
    values = ["aws-controltower-PrivateSubnet3A"]
  }
}

data "aws_subnet" "selected-2" {
  filter {
    name   = "tag:Name"
    values = ["aws-controltower-PrivateSubnet1A"]
  }
}

resource "aws_directory_service_directory" "rule-731" {
  name     = "corp.notexample.com"
  password = "SuperSecretPassw0rd"
  edition  = "Standard"
  type     = "MicrosoftAD"

  vpc_settings {
    vpc_id     = data.aws_vpc.selected.id
    subnet_ids = [data.aws_subnet.selected-1.id, data.aws_subnet.selected-2.id]
  }

}

resource "aws_fsx_windows_file_system" "valid-fsx-1" {
  active_directory_id             = aws_directory_service_directory.rule-731.id
  subnet_ids                      = [data.aws_subnet.selected-1.id]
  throughput_capacity             = 1024
  automatic_backup_retention_days = 15
  storage_capacity                = 1200
}

resource "aws_fsx_windows_file_system" "valid-fsx-2" {
  active_directory_id             = aws_directory_service_directory.rule-731.id
  subnet_ids                      = [data.aws_subnet.selected-1.id]
  throughput_capacity             = 1024
  automatic_backup_retention_days = 30
  storage_capacity                = 1200
}