[Observium] Storage check entity

Hi,

Ive googled and not seen the answer to this. Can I check only a certain partition in the entity section?

Also, if I use the storage_used or storage_free is that in megabytes, gigabytes, kilobytes, etc? I don't see any examples, it seems everyone is using the percent one but I have a single partition I want to check based on size since it's very large and percentage would be a huge variable.

Thanks