[mioelnir]

...and nothing happened because it does not retroactively dedup existing data?

Over time it would become horrendously slow, I agree, since you have too little RAM by a factor of at least 8.

[snuxoll]

And this is why ixSystems disables access to the dedup switch on their TrueNAS systems without contacting support to enable it.

I've got 30TB of small files stored on our TrueNAS system at work, there's no benefit to enabling it but if someone decided to toggle it we'd quickly learn there isn't enough RAM in the world to handle billions of 1-16KB files....