apache pulsar: storage write latency vs publish latency

Question

While looking at the metrics for the broker, I found there are two different latency metrics in pulsar broker: storage write latency and publish latency. I'm aware of the fact that apache pulsar in general guarantees <5ms for publish latency and I've sort of confirmed that on AWS(I ran my own benchmark) Nonetheless, storage write latency metric somewhat confusing as shown below as this does not fall sub 5ms in general. It would be helpful if anyone could explan what storage write latency means specifically and where(zookeeper, bookeeper, broker etc) it comes from.