emptyDir memory vs disk

General Discussions
1

In emptyDir, medium is divided into memory and disk. No matter which one, cache will be occupied. In the k8s environment, cache+rss = wss. Under what circumstances will disk be used? Is it that only active cache memory is stored in the disk?

Cluster information:

Kubernetes version:
1.26
Installation method:
Host OS:
CNI and version:
CRI and version:

2

With a disk volume, the data can be flushed from memory any time the OS wants, and reads might be disk-speed. With memory, it’s always in memory.