Failover is meant to deal with hardware failures, which will tend to work just fine. But if the node you are failing over onto was already has 60% capacity and you add another 60% capacity during the failover, things are going to get worse.

The top-level systems probably need to be able to deal with increased latency or timeouts, and properly handle retries and throttling of traffic.

If you have some HA failover setup going but your alternate is already being used more for load balancing than for failover, problems like this will occur.

(I used to work on failover drivers for a SAN).