I created pod on k8s cluster, and found pod is killed and it's Linux mahcine is failed to ssh login. when I restart the k8s node, I found the nodes home path is used for 90%. And I found the pod's log for /val/log/maillog is used 3T,why?

pwd

/home/docker/runtime/overlay/c5b8d2bd508ab41057d151aebc55cee707a44a704cbddba268ec929ff7e80542/upper/var/log

du -sh *

2.9T    maillog 
4.0K    messages

tail -n 2 maillog

> Apr 10 23:19:15 visbox1 04-10T23:19:15.417908+08:00 visbox1
> 04-10T23:19:15.417846+08:00 visbox1 04-10T23:19:15.417789+08:00
> visbox1 04-10T23:19:15.417734+08:00 visbox1
> 04-10T23:19:15.417675+08:00 visbox1 04-10T23:19:15.417582+08:00
> visbox1 04-10T23:19:15.417526+08:00 visbox1
> 04-10T23:19:15.417467+08:00 visbox1 04-10T23:19:15.417409+08:00
> visbox1 04-10T23:19:15.417355+08:00 visbox1
> 04-10T23:19:15.417300+08:00 visbox1 04-10T23:19:15.417243+08:00
> visbox1 04-10T23:19:15.417149+08:00 visbox1
> 04-10T23:19:15.417091+08:00 visbox1 04-10T23:19:15.417035+08:00
> visbox1 04-10T23:19:15.416978+08:00 visbox1
> 04-10T23:19:15.416920+08:00 visbox1 04-10T23:19:15.416858+08:00
> visbox1 04-10T23:19:15.416796+08:00 visbox1
> 04-10T23:19:15.416739+08:00 visbox1 04-10T23:19:15.416684+08:00
> visbox1 04-10T23:19:15.416627+08:00 visbox1
> 04-10T23:19:15.416574+08:00 visbox1 04-10T23:19:15.416507+08:00

the visbox1 is the name of pod