Ideal Opensearch Cluster?

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
I have Opensearch 1.3.8 - I will update this cluster to Opensearch 2 after some Optimization

Describe the issue:
We have like 70% allocation on hot and 90% on warm nodes. We need to expand.

Configuration:
We have 3 warm nodes, 3 hot nodes and 3 master nodes.
On data nodes, we have 32GB heap in docker, 50GB RAM for docker allocation and 64 GB on OS.
I think we have no problem with Heap and GC.

  1. But I need to expand allocations. We have 1 TB for HOT and 6 TB for WARM.
    Can you give me some tips? I need like 6 TB on SSD and 30 TB on WARM, at least, maybe 50 TB.
    Should I add 3 hot and warm nodes with same configuration or can i extend storage from 1 to 2 and from 6 to 12 TB?
  2. I have 3 datacenters and one node in every datacenter. What if I will have maintenance in one datacenter and I will stop this datacenter. If I had 6 hot nodes, 2 of them will be here and I shut them down. I use 1 master and 2 replicas shards. So If I will have only 4 nodes up, they maybe rellocate to other nodes and there would be big traffic and maybe no space left. Can I make somehow that 1 shard will be in every datacenter? If I shutdown 2 nodes in the same datacenter I will have 2 shards of every index still ready. Thanks

Can anyone help me please?

If cpu utilization is moderate, you can add just storage.
You can disable allocation during maintenance to avoid shard relocation.