The public cloud itself allows the OS to be installed to the instance drive. In addition to this you can have an external network drive added to the instance itself. This will provide you with external drive capacity. You can use this drive capacity to store files which you can unlink from the default server to another server. It can serve as a removable storage from instance to instance within the same datacenter.
Instead of using this storage as an external drive for storage, you can use it as a boot disk. You would first create an normal instance with all the boot details such as the master template information. As this is booting directly as an instance it will also boot from the disk when we make it later on.
Now we need to login to our horizon at: Horizon portal, once we have logged in, we can make a snapshot of the instance which we currently have. In essence this is a backup of the instance currently running.
When the snapshot is completed we can restore the snapshot as a volume and setting this into the boot disk. We will link the disk as a normal disk but to also set the boot flag. Once the instance reboots it will seek the boot disk first. If there is issues on the boot disk it will revert back to the instance OS.
You can also delete the instance disk so that the instance disk is seen as an external disk in the perspective of the OS.