You&#x27;re probably thinking of dedup, a ZFS feature that is off by default.<p>Dedup is only useful in certain specialised situations, so leave it off unless you have evidence it&#x27;ll result in substantial space savings (and you&#x27;re willing to deal with the memory footprint).<p>In my experience, ZFS&#x27;s RAM usage is reasonable, regardless of disk size, as long as you stay away from dedup. Most of ZFS&#x27;s memory usage is the ARC (the disk cache), which is what any OS more advanced than DOS does.