Late 2014 MacMini with combo SSD + HD Fusion Drive

Usually runs great, about 3x a day I can hear the HD really doing a lot of activity, reads / writes.

What can I use to determine which process is doing all of these reads / writes? I really want to find out what kind of diagnostics tool I can use to pinpoint what is doing all the reads / writes. I found some commands searching but those required booting into safe mode, I assume there is something I can use that doesn't require safe mode.

I can see from Activity Monitor that the IO spikes, but I cannot see a way to include a Read / sec column to activity monitor. Assume I need to use something else.

Image 1 shows high disk usage, image two shows it settling back down. For context on total IO: Time since boot: 26 days 22:20

Thanks for the help.

High IO Normal IO enter image description here

  • FYI Added the backup after this problem started happening in case disk is failing or system fails. Still need to root cause it in case backup has the same issue. – cjburkha Apr 28 at 12:23
  • You're not going to get individual transfer rates for each app - that's not the way it works. That measurement is for the disk as a whole. That said, what is it that you're looking for that Activity Monitor isn't presenting you? – Allan Apr 28 at 13:31
  • I am trying to see which app is responsible for the increased IO. I understand I probably cannot use Activity Monitor, looking for alternatives or command line commands that work without booting into safe mode. – cjburkha Apr 29 at 14:28
  • Activity monitor does in fact tell you which app is responsible for the most disk activity. Reading is a lot less intensive than writing and both of those values are presented. – Allan Apr 29 at 14:34
  • OK I am looking for a "what is writing to disk right now" metric. Or last 10 min. The data graph at the bottom is perfect but I want to see per app. – cjburkha Apr 29 at 16:34

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