EDIT - 20201206 @ 2216 UTC-7 - Added how to remove a hard drive and replace it with a bigger one to upgrade. EDIT - 20200311 @ 1859 UTC-7 - Added how to replace a dead hard drive in a btrfs pool.

EDIT - 20191104 @ 2057 UTC-7 - Figured out how long it takes to scrub 40TB of disk space.  Also did a couple of experiments with rebalancing btrfs and monitored how long it took.

A couple of weeks ago while working on Leandra I started feeling more and more dissatisfied with how I had her storage array set up.  I had a bunch of 4TB hard drives …