High Sierra Slow Bootup

Ever since I installed macOS High Sierra on my Late 2012 iMac the machine has booted up very slowly. It stays at a white screen for about 1 minute, then the boot progress bar appears. The boot progress takes at least another 30-45 seconds. That my friends is slow! I have tried all kinds of things and finally found the solution.

Trim and 3rd Party SSD’s

I have all kinds of drives and other USB devices connected to my iMac. I thought it might be one of these items that was slowing things down so I did a series of Restarts while connecting and disconnecting all of them. This did not affect my bootup time in any way. I ran all kinds of utilities on my machine which did not help either. So, I broke down and started doing research on the Web and came across what might be the solution, at least it was for me. The solution was not a one off, I located articles advocating this fix in several different places.

As you may recall, a few months ago I installed a Crucial MX300 SSD in my iMac. It made the machine much faster. I had been reading a lot about turning on the Trim function which is supposed to help keep SSD’s cleaned up and maintained.1 So, I used the Disk Sensei App to turn on Trim for the Crucial MX300 SSD.

Now, my research online revealed that having Trim activated for 3rd Party SSD’s in High Sierra causes the slow bootup. At this point, I would try anything to restore my machine to a decent boot time. I went into the Disk Sensei App and turned off Trim Support for my internal Crucial Drive:

Of course, after you do this you have to do a Restart. Man, was I surprised! I still had the wait at the white screen, but that only lasts about 20 seconds. Then, the boot progress bar appears and the machine boots up in about 15 seconds from that point. What a giant improvement! Here is what the System Report says about my Crucial Drive now:

If you have Activated Trim Support on a 3rd Party SSD using the Trimforce command in the macOS you just have to disable it:

Open your Terminal App and type in “sudo trimforce disable” (without the quotes). You will be taken through a series of questions that you answer “Y” Yes to, then the computer will reboot.

So, am I worried that Trim is not working on my SSD? Well, not really. I think Trim is good to have working if it works well with your 3rd Party SSD in High Sierra. However, most SSD manufacturers today have built in maintenance routines into their SSD architecture. Here is what Crucial says about their SSD’s:

Since not all operating systems support TRIM, Crucial SSDs have a special feature called Active Garbage Collection. Active Garbage Collection is a process that helps an SSD maintain optimal performance by freeing up memory sectors that are no longer in use. Garbage collection is part of the SSD itself and thus not dependent on your computer’s operating system. Since garbage collection is part of the SSD’s firmware, it works regardless of which operating and filing systems your computer is using.

I think this will have to be good enough for me for now. Most of the time my iMac stands idle during the evening hours and sometimes all night. This should be enough time for the Active Garbage Collection to do it’s thing.

I want to make one more observation here. Yes, my iMac starts up much faster than before. However, I have noticed that all the processes on the iMac are a smidge faster as well. The machine is just a little more responsive since I turned off Trim Support, YMMV.


Well, that is my story and I am sticking to it! You may not wish to turn off Trim Support on your 3rd Party SSD, but if you are having slow bootup times it might be worth it to just try it. You can always turn it back on again if there is no change.

  1. For more on how Trim works go to this article https://macessence.com/category/mac/disk-sensei/