Slow hard drive after OS update
Since upgrading to Sonoma 14.2, my iMac has been very sluggish. Using TechTool to measure the read/write speeds of the internal fusion drive, I get speeds of around 25–50 MB/sec when booting from that drive. When I boot from the external USB drive, the fusion drive measures around 110 MB/sec, which suggests to me that the problem may be software-related. On the other hand, the USB drive consistently measures around 200 MB/sec, whether or not I'm booting from it, and not having measured these drives before, I don't know their historical speeds. I did find that the fusion drive was a bit faster after a safe boot. EtreCheck reported the performance as "below average" after the safe boot and "poor" after the normal boot. Another thing that may well be relevant was that I tried reinstalling the OS to see if that solved the slowness problem (this was before I measured any speeds). In so doing, after the reinstall completed, the fusion drive—both the mechanical and the SSD—was in some sort of an unknown state and needed to be reformatted. After getting back to Sonoma, I restored all the apps and documents for a Time Machine backup, so if there was anything weird with these files, it's still present. I'm looking for comments, shared experience, or other advice you might have. Thanks.
iMac (2017 – 2020)
