People love to rag on SMR disks, but they have their uses.
I have a remote backup server that all it ever does is - once a night - receives an incremental block level backup stream at WAN speeds.
I'm going to need new drives for this server at some pointsnf when I do, I'll probably save a buck or two by going with SMR drives. My home NAS uses only CMR, but fot this remote backup purpose, SMR is great.
It won't be these disks though. They are both larger and use more power than what I need in this role. I'm thinking 5400rpm SMR drives, at maybe 8TB a pop.
Right now the backup server has 16x 4TB WD Red's in a RAIDz3 configuration. I went up on the redundancy due to it being remote and possibly being a longer lead time before ai can replace a failed drive. I also went single VDEV with many drives because the performance impact of this compared to multiple striped smaller VDEV's didn't matter much in this remote backup role.
That said, I could achieve the same storage capacity with a lot fewer of these 7200rpm huge drives. I'll have to run the numbers on purchase cost and power savings and see which is more favorable. 16 smaller, cheaper more efficient drives vs fewer larger more expensive, more power hungry drives.
I mean, 16x 8TB drives in RAIDz3 gives me 104TB.
If I stick with RAIDz3 I'd only need 7 of these big 26TB drives for the same capacity...
I haven't seen the price of these bad boys yet, and WD hasn't even released an 8TB SMR Red drive yet, so a proper comparison will have to wait.
I'm still only at ~65% capacity on the 16 4TB's so I have some time, but some of those drives are starting to get close to the 70k hours of uptime mark... At some point they are going to start dropping like flies...