If there's higher redundancy, then they are already giving up on density.

We've pretty much covered the likely ways to calculate parity.

I would think most standard consumers are not using HDDs at all.

It's like the petronas towers, everytime they're finished cleaning the windows they have to start again

You usually scrub you pool about once a month, but there are no hard rules on that. The main problem with scrubbing is, that it puts a heavy load on the pool, slowing it down.

Accessing the data does not need a scrub, it is only a routine maintenance task.
A scrub is not like a disk cleanup. With a disk cleanup you remove unneeded files and caches, maybe de-fragment as well. A scrub on the other hand validates that the data you stored on the pool is still the same as before. This is primarily to protect from things like bit rot.

There are many ways a drive can degrade. Sectors can become unreadable, random bits can flip, a write can be interrupted by a power outage, etc. Normal file systems like NTFS or ext4 can only handle this in limited ways. Mostly by deleting the corrupted data.

ZFS on the other hand is built using redundant storage. Storing the data spread over multiple drives in a special way allowing it to recover most corruption and even survive the complete failure of a disk. This comes at the cost of losing some capacity however.

It matters to me. I got stuff to back up regularly, and I ain't got all weekend.

The only flash drive I ever had fail me that wasn’t made by sandisk was a generic microcenter one, which was so cheap I couldn’t bring myself to care about it.

Yeah, lots of drives of varrying capacity.

Thank you for all this information. One day when my ADHD forces me into a making myself a home server I'll remember this and keep it in mind. I've always wanted to store movies but these days just family pictures and stuff. Definitely don't have terabytes but I'm getting up 100s of gb.

I remember renting a game, and it was on a high density 5.25" inch floppy at a whopping 1.2MB; but or family computer only had a standard density 5.25".

So we went to the neighbors house, who was one of the first computer nerds (I'm not sure he's still alive now), who copied the game to a 3.5" high density 1.44MB disk, then we returned the rental because we couldn't play it on the 1.2 MB HD 5.25" floppy.

.... And that was the first time I was party to piracy.

It's only the first copy that takes such a long time. After that you only copy the changes.

That depends entirely on your usecase.

Sure, if you have many TBs of data changes per day you probably want a different solution. But that would also suggest you don't need to keep it for very long.

Write speeds on SMR drives start to stagnate after mere gigabytes written, not after terabytes. As soon as the CMR cache is full, you're fucked, and it stagnates to utterly unusable speeds as it's desperately trying to balance writing out blocks to the persistent area of the disk and accepting new incoming writes. I have 25 year old consumer level IDE drives that perform better than an SMR drive in this thrashing state.

Also, I often use hard drives as a temporary holding area for stuff that I'm transferring around for one reason or another and that absolutely sucks if an operation that normally takes an hour or two is suddenly becoming a multi-day endeavour tying up my computing resources. I was burned once when Seagate submarined SMR drives into the Barracuda line, and I got a drive that was absolutely unfit for purpose. Never again.