I'm running a Mac Mini 2014 with High Sierra (10.13.4) and am experiencing some lag, since adding a pair of Thunderbolt RAID drives. I've also added 25 or so SMB sharing users. Only a few users are active at any time, and mostly through Sharing, not logging in.

The lag is apparent in the Desktop when I'm logged in, and in initial delay, when I access an SMB share.

A couple of questions:

  1. How can I determine which maxed-out resource is causing the lag?

    • Is it RAM (I've got less than a GB of swap in used)
    • Is it CPU (I'm idling at less than 5% usage, but still see the lag)
    • Is it Disk or throughput to disk? (I've got 15/18 TB free on the RAIDs and 210/252 GB free on the OS drive)
    • Is it network? (I see mostly a number near 0 for packets/sec, with bursts higher)
    • something else?

    The only resource that seems stressed at first glance is cached files: 2.6GB.

  2. Is there a way to manage (change priority, stop) some system services to free up more resources for file sharing?

  3. Is ther a way to tune smbd so that it's more responsive? (I don't care about the console performance, as long as I can admin the system occasionally)

Update: I received several user complaints about performance. Not knowing what else to do, I restarted the machine. Looking at Activity Monitor, now, I see that it memory usage has changed - it's no longer using any Swap. Not sure why yet. Nothing was intentionally changed.

  • Your statement "which maxed-out resource" confuses me. Are you saying that the RAM, CPU, Disk, Network etc. are maxed out at any time? Do you see the lag when only one person is connected? How are people connecting?
    – Allan
    Apr 20, 2018 at 17:05
  • I guess I'm assuming that the lag I'm experiencing is due to a stressed resource. Maybe not? I always see some "unexpected" lag which leads me to think I could fix it. The lag decreases after 5pm when users start going home.
    – Matt
    Apr 20, 2018 at 17:07
  • 1
    Unless you see a maxed out resource, you shoudn't assume it to be the case. Hook a computer via Ethernet to the mini and try some file transfers. See if there is lag. If not, hook some more up and test again. Are your clients wired or wireless?
    – Allan
    Apr 20, 2018 at 17:10
  • Before you added the T-bolt RAID, what were you using for file storage?
    – IconDaemon
    Apr 20, 2018 at 17:12
  • 1
    It could be anything. If there's inherent latency, you'll see it with a single user. It could be the network, it could be the drive(s) sleeping, it could be any number of things, but it's best to get a base line and start from there. By going directly with Ethernet, you're removing the latency of a wireless connection (nothing's more stable than a physical connection).
    – Allan
    Apr 20, 2018 at 17:19


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