ZFS doesn't really need huge amounts of RAM. Most of the memory usage people see is the Adaptive Replacement Cache (ARC), which will happily use as much memory as you throw at it, but will also shrink very quickly under memory pressure. ZFS really works fine with very little RAM (even less than the recommended 2GB), just with a smaller cache and thus lower performance. The only exception is if you enable deduplication, which will try to keep the entire Deduplication Table (DDT) in memory. But for most workloads, it doesn't make sense to enable that feature anyways.