Good filesystem for the nix store

[SRGOM]

I catalogued my zfs usage here:

Zfs dedup on /nix/store -- Is it worth it?

Recently I’m experimenting with several zfs features, I learned that zfs can do block level deduplication. Has anyone tried it on /nix/store? Since we already have nix optimise-store, can I still benefit from the block level deduplication? The deduplication implementation of zfs lowered the write performance, but /nix/store is read-only in most of time, I think it doesn’t matter, am I right about that?

In short, despite autoOptimise on, I had a dedup of 1.35.

(I’ve turned off autoOptimise now)

I should also note that in my system of 8GB ram, nix-env --install irrespective of size of derivation are regular but nixos-rebuild takes my RAM usage from 30% of 98% and the system comes to a stand-still. I am not sure how to explain this …