V 6.40 Even when sending files to my device (save to disk), I found that my A/V was being hit heavily
I had excluded the Device drives (I locked the letters, and verified they were still correct).
I excluded the library.
I (unhappily, excluded a live program) C:... /calibre2
Calibre is using other file-space somewhere that triggers a real time scan of it'sactivity.
Disabling A/V was the only thing that dropped the usage and really improved performance.