• Besides the issues already listed, in my experience network (interface) is where i would meet the beachball very often. For one, nowadays with 802.11ac, fiber-optic i’d expect instant display or refresh of every network access -and frustrated when it’s slow. When this is the case, I found out that the Mac is not at fault half of the time: my ISP router is the culprit for that half. It has dual channels with ‘ac’ and ‘n’, and while ac is faster most of the time, from time to time it mysteriously slows down the whole house! Sticking to ‘n’ is not the solution because the mysterious slowness happens with that too. The solution for me is to switch from whatever channel i’m using to the other when slowness occurs, and refresh. I also have to switch before doing an important network op, e.g. sending an important e-mail, access/post a form online… because recovery or refresh does not work in most of these cases.

  • macOS Sierra added another helper for reclaiming disk space. The Manage button on the About this Mac dialog can purge unnecessary files and may also suggest moving some of them to iCloud.

  • iDefrag is helpful too, especially with pure hard drives. While file fragmentation isn’t an issue anymore, files being scattered all over the drive, especially system files, can make a huge dent in latency and cause a lot of “beach ball of death”. Reinstalling the OS accomplishes the same thing by pulling all the data off the drive and writing it back in a logical order.

  • I’m running Sierra on an older iMac (mid-2010). When I goto AboutThisMac->Storage, I get a bar for “Macintosh HD” which says “Calculating…”. The “calculating” never completes. Is there a config parameter I have to change, to make this work?