AWS change EBS root volume on data collection system - amazon-web-services

Question

I have the following use case:
I have an EC2 instance running with an 1000GB io1 SSD EBS root volume attached
It is used for a data collection service which accumulates data every minute
I like to change the volume for a cheaper storage system (as the specs of the process are not IOPS intensive)
I've read through the AWS documentation and found the following articles:
https://aws.amazon.com/about-aws/whats-new/2017/02/amazon-elastic-block-store-amazon-ebs-enables-live-volume-modifications-with-elastic-volumes/
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-expand-volume.html#console-modify
Which indicate that (from february 2017) for Current Generation Instances a volume type change is possible on the fly in the console without stopping the instance. However, when I go to my console I can only choose between io1 (current) or gp2 (also SSD), I'd like to choose sc1 (cold storage) for this instance. The video clearly shows this option (go from io1 to sc1).
Am I missing something? Is there a restriction to go from SSD to HDD?
(im in Asia Sydney region).
Alternatively, if the option is not possible and i have the requirement that data collection continues, it seems that my only option is:
re-create a similar instance with the data collection scripts deployed with an EBS sc1 volume as root attached
get the data collection running (now collecting double)
stop the old instance and take a snapshot of the io1 EBS volume
create a EBS sc1 volume with the snapshot
attach the EBS sc1 volume to the new instance (as additional volume, not root)
Would this be the right way to do so? (if I can't change the volume type to sc1 while it's running)

Answer 1

tldr;
The 2 main reasons why amazon will not propose sc1/st1 type when editing the EBS volumes are:
the current volume is used as root device of the ec2 instance
the current storage is less than 500 Gb
I guess the volume you want to change is used as root device of the instance; in this case you cannot have boot volume of magnetic type st1 or sc1.
Note also the sc1 volume must be at least 500 Gb
You can read more about EBS Volume Types
Unfortunately, you cannot change the root device of a running instance, you can do that while the instance is stopped.
so you can follow your steps proposed but you can make the change of the EBS after it will be detached from the first ec2 instance
re-create a similar instance with the data collection scripts deployed with an EBS sc1 volume as root attached (You cannot have sc1/st1 drive as boot volume; if you want magnetic storage you need to select standard Magnetic storage; but ideally you should have a low volume ssd drive as boot volume and the large magnetic drive as additional ebs volume)
get the data collection running (now collecting double)
stop the old instance and detach the EBS volume
make the modification of the EBS volume (type/storage)
attach the EBS sc1 volume to the new instance (as additional volume, not root)