Sorry, I definitely meant mirror and not replica. I’m sleepy today.
Regarding the pool design, I’m open to hear it, but I don’t think I’m open to RAIDZ, I considered that for a while, let me explain:
- MARS is 4TB, almost full (75%)
- VENUS is 4TB at 45%
- JUPITER is 14TB at 13%
Content:
- MARS has jails + media files
- VENUS has family photos (very important), documents and media files
- JUPITER has media files so far (and it’s mostly empty)
- EARTH has backups of other computers
- URANUS has throwaway data, not really relevant
The reason why I didn’t go with a RAIDZ are the following:
- I don’t trust my skills as a TrueNAS admin. Confirmation of that is how I messed up some data on MARS
- Turns out I get very stressed with backups, having a full mirror makes me way more confident if something goes wrong at the hardware level
- I purchased the HDDs over a very long timeframe (~6 years), I didn’t really know I was going to buy a 14TB drive
- I really appreciate the simplicity of saying “if something goes wrong, clone the HDD”, without having to deal with multiple HDDs. I can do a raw clone from any system and it would be fine
- Read performance is the only relevant one given the large amount of media files
- I have 24 HDD slots on my server and currently use 8
I’m open to hear a different opinion, but my stress level goes really high when I think about the fact that if I lose X drives, I lose all the data that I have ever owned. Having it spread in this way gives me more confidence that at least I won’t lose all the data at the same time.
As you can see, stress is my major driver 
EDIT: Forgot model numbers. This screenshot doesn’t include backup drives:
- MARS has 1 HDD green for backups
- VENUS has 1 HDD green for backups
- JUPITER has 1 HDD Exos enterprise for backups: ST14000NM001G
I also have a spare 8TB Exos enterprise HDD