In practise any strong encryption (ie, not AES-ECB) is indistinguishable from random noise, and that's by design. Even trying to de-duplicate 4kb blocks of rand

In practise any strong encryption (ie, not AES-ECB) is indistinguishable from random noise, and that's by design. Even trying to de-duplicate 4kb blocks of random noise would be a completely fruitless task. If it was possible, storage is probably cheaper than the CPU time to find similar blocks.