Dedupe is an optional and often misunderstood feature. It's a solution to a niche problem and not something you should enable because it exists. Data protection doesn't require lots of memory, but the way it's implemented means you can't just use the file system cache to back memory mapped files 1:1 like you can with a less reliable file system that modifies file content in place without checksumming. ZFS doesn't have to be the memory hog it's made out to be. A lot of the issues with ZFS on 32bit systems come from the fact that pre Meltdown the kernel heap had to fit into <1GiB of the address space shared with memory-mapped I/O. Often its cache hat to be restricted to ~300MiB and tried to allocate 128kiB continuous buffers from that since it was designed for 64bit virtual address spaces there was no support for chaining multiple smaller allocations to back a large block.