Depending on how the mem-table is implemented, they can write at practically RAM-speed.
Proof needed I think. When last I looked I could get it to just under a gib/s. The disk itself could do 2-3 and ram is 20.
It’s fast but it’s definitely a long long way off from RAM speed. The reason is that the memtable is quite pricey to maintain - you’re having to constantly keep a non trivial amount of data sorted and that sort is expensive.
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Proof needed I think. When last I looked I could get it to just under a gib/s. The disk itself could do 2-3 and ram is 20.
It’s fast but it’s definitely a long long way off from RAM speed. The reason is that the memtable is quite pricey to maintain - you’re having to constantly keep a non trivial amount of data sorted and that sort is expensive.