Cloudformation Ephemeral (Instance) Storage for instance

Question

I am trying to launch an EC2 Instance with CloudFormation that uses ephemeral / instance storage rather than EBS.

I have managed this with Opsworks - so that in the EC2 management window "root device" is not ebs. I have yet to figure out how to do this with a CloudFormation template.

I have a feeling it has something to do with BlockDeviceMappings but have not figure it out yet. Closest discussion to what I want to do I found here: https://forums.aws.amazon.com/message.jspa?messageID=243921

Can someone supply a CloudFormation template snippet to launch a ephemeral storage based instance?

Other parts of the docs that seem useful:

• http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-blockdev-template.html
• http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-blockdev-mapping.html
• http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-instance.html
• http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/quickref-ec2.html

Answer 1

I am not sure what OS you are trying to launch, but the key is that you have to use the right AMI. For example, look at Canonical's AMI listings for Ubuntu: http://cloud-images.ubuntu.com/locator/ec2/

If you search for precise us-east-1 you'll see there are 5 different AMIs:

us-east-1   precise 12.04 LTS   amd64   hvm             20130624    ami-25d9a94c    hvm
us-east-1   precise 12.04 LTS   amd64   ebs             20130624    ami-23d9a94a    aki-88aa75e1
us-east-1   precise 12.04 LTS   i386    ebs             20130624    ami-21d9a948    aki-b6aa75df
us-east-1   precise 12.04 LTS   amd64   instance-store  20130624    ami-d9d6a6b0    aki-88aa75e1
us-east-1   precise 12.04 LTS   i386    instance-store  20130624    ami-bfd3a3d6    aki-b6aa75df

The first one is for cluster compute instances only.

The second and third are for EBS-backed instances, 64bit or 32bit.

Finally, the fourth and fifth are for ephemeral / instance storage backed instances, 64bit or 32bit.

Once you have chosen an AMI that is instance-store backed, you can assign the rest of the emphemeral disks with this snippet inside the Properties:

"BlockDeviceMappings": [
    { "DeviceName": "/dev/sdb", "VirtualName": "ephemeral0" },
    { "DeviceName": "/dev/sdc", "VirtualName": "ephemeral1" },
    { "DeviceName": "/dev/sdd", "VirtualName": "ephemeral2" },
    { "DeviceName": "/dev/sde", "VirtualName": "ephemeral3" }
],

You may want to review the AWS block device mapping concepts page as well.