Experiencing a sudden loss of performance on your file server – defragsvc very high 100% disk usage
Came across users reporting an apparent slow down in file access speeds at a site today, having checked the server in question the disk activity was very high 100% disk usage time.
Drilling further down it was identified to be svchost.exe (defragsvc) that was running a Defragment and Optimise on the main 4TB data disk. Opening %windir%\system32\dfrgui.exe and stopping the scan immediately brought the server back to normal.