Currently hash rates of two stratum are not merged.
But very soon we will launch multiple stratum server with merged hash rate.
In this setup we will place stratum, website and payment core in different server or different ISP.
And we will have multiple stratum servers.

After this migration,
* DDoS on stratum or website does not affect other server.
* Even if all stratums are down by DDoS, we can create more stratums easily in a short time in other ISP.