If you need a *lot* of storage capacity (more than eight drives’ worth), take a look at 45Drives. They make physical enclosures based on the Backblaze Storage Pod design. Their main line has rows of 15 3.5” drives (the original design had three rows, hence the name). They make boxes with one, two, three, or four rows. Even the single-row box is pretty big, but all the active parts are off-the-shelf, so it’s very serviceable. No dependency on a particular vendor.
You can get similar results building a system yourself with a desktop case, but the 45Drives systems are a bit nicer.