Lenovo E530 11e E/Edge :: What Is Express Cache Supposed To Do

I have E530 with 1TB disk and 16GB mSSD disk, which is partioned in 2 partitions. Now, I suspect Express Cache is using it somtimes, but I never see any usage from it in Task Manager. Task Manager Screengrab.However, sometimes Express Cache goes nuts on my HD, doing the opposite of what it is supposed to be doing Resource Monitor Showing Express Cache thrashing my HD
 
However, it seems to be doing something, sometime. I suspect it is from rebooting, but I rarely reboot my computer, so I'm not gaining much from it. I just formatted that mSATA drive and perhaps put the windows swap file and perhaps other cache folders there? I always feel that the disk I/O is the bottleneck of this computer, it feels slow when accessing the disk.