Disallow mixed device type on the same pool? #549
Description
In the hope to bring a good user experience, I'm wondering if Stratis should refuse to create a pool with mixed-type devices. For instance a pool with HDD and SSD. It's probably best to have an SSD pool and an HDD pool instead of mixing both. Performance is the main driver for this request, it would be strange to have a pool with sporadic performance depending on which blockdev the fs ends up being created. One thing that we could benefit from is adding a 'type' or a 'class' to a pool to identify its performance characteristics or guess at a glance.
Thoughts?