Why are queries getting slower and slower

Elastic Stack Elasticsearch
1

Before Oct 18, static 99% less than 439ms, After Oct 18 is 603ms.
cluster: 5 node mdi, 32core 128G memory(but jvm config is 31g). 1 index 100shards,2b documents with 2T disk used space.

Is it because there's too much documentation?

2

Disk I/O is often a limiting factor in Elasticsearch. What does it look like in your cluster, e.g. using iostat? Has your data set grown or changed?

3

Thanks.
I find that the I/O usage rate is indeed soaring.
Could you tell me how to improve this situation?
Add more nodes?