memory usage grows as storage volume grows

[ghost]

I hope this is still alive and running, regardless I'm seeing a strange issue.
Basically I was switching from old nfs storage to this new storage. I mounted the pvc as a volume called backup on the container. Then just did an rsync from old directory to the new when the container crashed OOM?
At first I was very suprised and thought it had to be something to do with the files? I tried many many tests after that. Tried spinning up a brand new container. Nothing on it. Add a pvc which is 8g. Then copied a 66mg file onto the container as a tar.gz. Its just a really big text file. Extract the file which becomes 1.5g. And as you imagine memory for the container spikes with the new data?

Is there something I'm missing? Please let me know if there is anything I can provide to help narrow this down.

kube version - v1.13.1