I've found the documentation hard to find, such as "type: hostdir" for storage pools. What is hostdir? Is this the only type of pool OpenEBS supports?
Their documentation is missing explaining what hostdir is in their StoragePool resource definition. Judging by this it's just a directory on your Kuberbetes nodes.
Also, they mention that there are 2 options: a directory on the host-os or a directory on a mounted disk. Either one of those 2 choices means that your directory will be on the node so it will be a hostdir, so I assume that's the only option available.
Hope it helps!