Code review comment for lp:~ltrager/maas/validate_storage

Thanks for the review. I've gone over and responded to your comments below. The performance issues you are seeing are all due to validating that / isn't on bcache. In order to check if a partition/block device is on bcache I need to check the parent devices. There isn't currently a relation between child and parent so I have to iterate over all the blockdevices the node has until I find the partition/block device in question.

There are only two ways I can think of that will improve performance
1. Modify the schema so we have a relation between child(virtual block devices, and partitions), and parent(block devices, partitions)
2. Don't check if / is on bcache.