Memory Allocation for Multi-instance SQL DB

Hi All,

I have installed a 2-node multi-instance (active-active) SQL failover cluster.

Here is the setup details:

1. Server1 (Node1) physical memory of is 64GB. Running Web_Instance01.

2. Server1 (Node2) physical memory of is 64GB. Running Web_Instance02.

I allocated 58GB maximum memory for each instance and the rest (6GB) is for Operating System.

Question:

If a failover happens and the 2 instances runs on the same server (example: Node1), does it mean that we require 116GB RAM on the Node1?

Anyone have setup similar environment? Do I need to manually configure each instance to allocate RAM after the failover?

Appreciate if anyone can point me to any links or resources regarding this.

Thanks in advance.

Regards,

Ivan