What would you like to be added:

Multiple active gateways for higher inter-cluster data transfer performance.

Why is this needed:

Currently there is only one gateway per cluster. As per the benchmark result in #2890, there is significant performance drop (about 56%) for PODs running on non-gateway nodes. Suppose the gateway node has a 10Gbit/s NIC. For DBMS servers running on non-gateway nodes, they only share 560 MByte/s. This means the whole cluster is only able to transfer 46TB of data per day at maximum, theoretically, which is unacceptable for productional clusters (JFYI, a small to median sized productional ClickHouse cluster can receive more than 40TB of data per day).