If you would like to launch an instance on AWS you have basically two options for root volumes:
- Instance Store backed root volumes
- EBS backed root volumes
So you cannot really use ephemeral storage as root disks. In conceptional point of view the Instance Storage is very similar to ephemeral one, but Cloudbreak does not support it mainly for the following reasons:
- Instance Store has slower boot time it is up to 5 mins, the esb is up to 1 mins according to specification.
- Instance Store has a limit in size which is 10GB which does not really make suitable for installing HDP packages on it
- a lot of base ami support EBS root disk only, e.g. I was not able to find Redhat 7.2 base ami with “Instance Store” support
You can read more about root disk storage on AWS site:
Cloudbreak supports EBS only and with a fixed size of 50GB, although this 50GB is not configurable at the moment, but based on a feature request we can make it configurable.
The ephemeral disks selected by you on Cloudbreak UI is used for HDFS data, so Cloudbreak puts the HDFS data on those ephemeral disks, but all HDP RPMs will be installed on the root disk with is EBS backed.