I'm working on something more similar to the Backblaze Storage Pod (in fact, originally based from their 2.0 design) for my employer. We played around with the hardware from their set up and decided to go a different route. It looks like we'll be getting 48 drives in 4U, but I'm sure we'll have some teething issues as we start to get our first few boxes up & running. 72 drives in 4U sounds like a lot of fun- I'm guessing SuperMicro SAS backplanes. Is there room in the box to make it self-sufficient or is it JBOD?