Terraform - creating multiple EBS volumes - amazon-web-services

Question

How would I go about creating and attaching more than one EBS volume to an instance?
The code below works when attaching a single EBS volume. My main concern is creating a map between the size of the EBS volume and the device name. I've tried a variant of things, creating a list, etc. But no luck.
# Create EBS volume
resource "aws_ebs_volume" "ebs_volume" {
count = "${var.ec2_create_volume == true ? var.ec2_instance_count : 0 }"
availability_zone = "${aws_instance.ec2.*.availability_zone[count.index]}"
size = "${var.ec2_ebs_volume_size}"
type = "${var.ec2_ebs_volume_type}"
}
# Attach EBS Volume
resource "aws_volume_attachment" "volume_attachment" {
count = "${var.ec2_create_volume == true ? var.ec2_instance_count : 0 }"
device_name = "${var.ec2_device_name}"
volume_id = "${aws_ebs_volume.ebs_volume.*.id[count.index]}"
instance_id = "${aws_instance.ec2.*.id[count.index]}"
}

Answer 1

You almost there, try using element(list, index) - it will loop over the list. For example, this config will successfully create 2 ec2 instances with 3 additional ebs volumes attached to each:
variable "ec2_device_names" {
default = [
"/dev/sdd",
"/dev/sde",
"/dev/sdf",
]
}
variable "ec2_instance_count" {
default = 2
}
variable "ec2_ebs_volume_count" {
default = 3
}
resource "aws_instance" "ec2" {
count = "${var.ec2_instance_count}"
ami = "${var.aws_ami_id}"
instance_type = "${var.ec2_instance_type}"
}
resource "aws_ebs_volume" "ebs_volume" {
count = "${var.ec2_instance_count * var.ec2_ebs_volume_count}"
availability_zone = "${element(aws_instance.ec2.*.availability_zone, count.index)}"
size = "${var.ec2_ebs_volume_size}"
}
resource "aws_volume_attachment" "volume_attachement" {
count = "${var.ec2_instance_count * var.ec2_ebs_volume_count}"
volume_id = "${aws_ebs_volume.ebs_volume.*.id[count.index]}"
device_name = "${element(var.ec2_device_names, count.index)}"
instance_id = "${element(aws_instance.ec2.*.id, count.index)}"
}

Answer 2

Incase anyone else is looking for the answer. The solution below works for multiple instances across multiple az. Here device_name is list of string so we need to pass as many names as the number of additional volumes and volume_count is the length of list of number additional_volume_size.
resource "aws_ebs_volume" "ebs_volume" {
count = var.instance_count * var.volume_count
availability_zone = aws_instance.ec2[floor(count.index/var.volume_count)].availability_zone
size = var.additional_volume_size[count.index%var.volume_count]
}
resource "aws_volume_attachment" "volume_attachement" {
count = var.instance_count * var.volume_count
volume_id = element(aws_ebs_volume.ebs_volume.*.id, count.index)
device_name = element(var.device_name, count.index)
instance_id = element(aws_instance.ec2.*.id, floor(count.index/var.volume_count))
}

Answer 3

Multiple EC2 instances with multiple EBS volumes of different sizes. This works with odd or even number of volumes.
instance_count = 3
ebs_volume_count = 2
ec2_ebs_volume_size = [10, 15]
ec2_device_names = ["/dev/sdd", "/dev/sde"]
variable "instance_count" {
type = number
default = 1
}
variable "ebs_volume_count" {
type = number
default = 0
}
variable "ec2_ebs_volume_size" {
type = list(any)
default = [
10
]
}
variable "ec2_device_names" {
type = list(any)
default = [
"/dev/sdd"
]
}
variable "availability_zones" {
type = list(any)
}
variable "subnet_ids" {
type = list(any)
}
resource "aws_instance" "ec2_instance" {
count = var.instance_count
ami = var.aws_ami_id
availability_zone = var.availability_zones[count.index]
subnet_id = var.subnet_ids[count.index]
instance_type = var.ec2_instance_type
}
resource "aws_ebs_volume" "ebs_volume" {
count = var.instance_count * var.ebs_volume_count
availability_zone = "${element(aws_instance.ec2_instance.*.availability_zone, floor (count.index/var.ebs_volume_count))}"
size = var.ec2_ebs_volume_size[count.index%var.ebs_volume_count]
}
resource "aws_volume_attachment" "volume_attachement" {
count = var.instance_count * var.ebs_volume_count
volume_id = aws_ebs_volume.ebs_volume.*.id[count.index]
device_name = var.ec2_device_names[count.index%var.ebs_volume_count]
instance_id = "${element(aws_instance.ec2_instance.*.id, floor (count.index/var.ebs_volume_count))}"
}