Very slow boot on Fusion and Big Sur

I've been struggling with this for days now.. and of course weeks prior with it getting slower and slower and not knowing what was going on. This now makes sense for my fusion drive mac.

One quick question as I test some of these ideas. When you guys have said to let boot and site idle for 30 minutes (or even an hour), then reboot and do again 2-3 times.... are we talking about letting it boot and sit at the user login screen for 30min+ then reboot? Or login your user and THEN let sit for 30+ min on the desktop and then reboot?

thanks

Can you please stop spamming these boards with advertisements for Etrecheck? It’s getting a bit much. With regards to this issue, nothing relevant has come out of it.

As far as upgrading to 11.3 goes:

I did a normal in-system update.

as posted above, after reboot I did see the new “optimising your Mac” notification

boot times have not improved. Boot to login screen: 1min, login screen to desktop: 2min10

I left the system idle overnight so it had plenty of time to reorganise files

The next morning I rebooted. Boot to login screen: 45s, login screen to desktop: 3min20 (!)

So it was even worse. Interestingly, I set the screensaver to kick in after 2 minutes. And yes: it started and played smoothly. When I moved the mouse, it kicked back to an unresponsive desktop (that was still not complete and beachballing).

if I find the time, I will reinstall the system from external media and see if that improves anything, but I can’t imagine it will.

This can be another interesting thing to do the next time I'll move big files or I'll install big programs. By the way, Activity Monitor by itself uses about 5% - 7% CPU and I'm not sure the Fusion Drive housekeeping processes can start when Activity Monitor is running.

No, indeed, we cannot be sure if that process (or processes) start when Activity Monitor is running, but there is a good chance they do if you leave the system idle after starting up Activity Monitor. Several other processes do run constantly even if you leave the system "idle" (i.e. if you don't start any app), so the Fusion Drive "housekeeping" process apparently ignores them when it's doing its work.

Performance wise, I noticed three major issues, one going beyond the slow boot times:

• Time from pressing the power button to the login screen: the progress bar would get stuck for a while, or the screen would go black, causing major delays (>1min).
• The most obvious one is after logging into my user account, it took several minutes to get to the desktop (>3min). The screen went black with only the mouse visible, then the desktop appeared in bits and pieces while beach balling. Now, the background never goes black. I only have 1 account and the login screen adopts the same background as the account, so the dock nicely slides in from the bottom and within 10s everything is responsive. The difference is day and night.
• While I assumed my system was fast after everything booted up (after all, I worked on it for 6 months), it clearly was not. Apps are now far more responsive: Safari, Mail, Maps, all appear within 1 icon bounce, often without a single bounce. Even the first time after booting the system.

When FileVault is enabled, the login prompt is shown at an earlier phase of the boot process, because the password is required to unlock the disk. Then when booting with FileVault enabled the login screen appears few seconds after you pushed the power button.

Back in 2017, The 2TD Fusion drive with 128GB of SSD was a substantial upgrade from the standard 1TB Drive. It offered a balance of capacity, performance and affordability. So now that Big Sur doesn't perform well with the Fusion drive, it's our fault that we didn't spend an extra $$$ for a 2TB SSD drive back in 2017.

Well, it's just seemingly strange that a proprietary OS can't support its own proprietary hardware fully, isn't it? And why market it in the first place before careful consideration for long term support? I didn't know about the existence of fusion drive until the current iMac purchasing online ordering steps. If just given the choice of HDD vs pure SSD at the point of purchase, I would have taken the SSD option since all my other machines were already on SSD.

https://en.wikipedia.org/wiki/Fusion_Drive

Thank you, but you haven't read the (admittedly) long thread completely, as it appears.

We have booted in safe mode, months ago already.

No login items are present, no launch daemons, no launch agents that can be called suspicious or unnecessary.

I'm willing to give step 3 a try, but I suppose you mean to move the cache files and the "saved application state" files to a new folder and then erase the original ones?

And Apple Care has been contacted before. In my case they were very helpful and put me through to a Senior Support Engineer, who confirmed that our problem had been acknowledged and was being looked into.

This new information has encouraged me to upgrade from Mojave to Big Sur on my 2017 27-inch iMac. Thank you, Tomeranary and Deep Sky Diver, for sharing your experiences, good and bad, and keeping us informed of your progress. Stay safe and well.

I've been following very closely on the issues arising after people with fusion drives upgrade to Big Sur and have been putting it off, and still am on Catalina. Do you guys recommend to do it now or wait for future Big Sur updates? If you recommend upgrading now or in the future, what is the approach and appropriate steps I should take?

Well, let's say that that my iMac (21" 4K late 2015) went from "always very nice" to a "total royal pain" in the space of only 4 months. Nothing new installed except Big Sur.

I do have the 2TB + 128 Gbb and it's mostly used by my wife to run office, spotify and browsing our photo library from time to time.

The computer is fairly old for "my" standards (I'm an IT professional) but this rapid deterioration is unheard off for an Apple device... are we back to "Vista upgrade experience" again?

I'm considering performing a clean install as well. But when I did that with 11.1, it didn't make any difference at all. The problem is that for my work I have photo and video software that is fine-tuned and has a number of plug-ins that need to be fine-tuned as well. Basically, doing a clean install takes me 2 days before everything is up and running again. I can't afford to loose so much time if I'm not 100% sure it will definitely solve the problem of such slow boot times.

VikingOSX: Yours is the most useless response I have ever seen in a forum. Should I have "bought" or hired an entire engineering department to fix my iMac 27?

But regardless, where is the solution to the slow startup with BigSur? Seven months later it still still very slow.

And not, it is is not only a startup application. I have no applications set up to start when I turn my computer on and still, not only the computer itself takes up to 10 min to start. Opening web browsers, Microsoft applications or (gulp!) Adobe apps takes such a long time that I have programmed myself to do other activities while everything is finally set up.

Alas, the buttons do not include a Not Helpful choice.

Mac OS has plenty of space to install on a 24GB SSD so you are incorrect. Glad you got yourself an external SSD that works, good solution for this Fusion drive owners.