Rebalancing ZFS Pools: Is It Necessary? 🤔

This video was sparked by a question @CoreyPL asked last week about whether I rebalance my pool after adding a new vdev. The short answer was "No," but I realized that the factors that get weighed into the decision might deserve more explanation than a comment could give!

So here we are! What exactly does it mean to "rebalance" a ZFS pool? Is it useful? What kinds of things do we have to think about, and are there other things we could do that might have more of an impact? Let's talk about it!

EXTRA CREDIT:
- My home NAS is more for bulk storage than any sort of high-performance activity like video editing or media streaming, so I actually don't have L2ARC or SLOG--but I absolutely use both of those device types in an enterprise context!
- If you do add a flash-based log vdev to your pool, TrueNAS does have tools to "re-size" your log device to a smaller size. This essentially allows the drive's flash controller to perform wear-levelling over more physical sectors of the device, which prolongs its lifetime in a high-write role!
- Thanks again to @CoreyPL for the great question!