Very slow boot on Fusion and Big Sur

Hi!

I may be able to give you some pointers.

Let's try:

1. Booting into safemode; https://support.apple.com/en-us/HT201262
2. let's delete (minus sign) login items: apple menu > system preferences > Users & Groups
3. Let's open Finder and go to menu, Go > Go to folder > ~/Library/Caches >>> select all (CMD + a) > new folder with selection, do the same for "Saved Application State" and reboot.
4. Still trouble? Let's create a back up and contact AppleCare!

Hope this helps,

Met vriendelijke groet / Best regards, Wempe

Careful if you let "Big Apple" know about "Big Sur" not being able to boot a one-year-old high-quality and very expensive iMac in less than 3,5 to 4 minutes... I already let them know 3 times since mid-November, and 3 months and 3 versions later still no fix, no acknowledgment of the existence of the problem, and if you dare to say anything else but purely "technical" stuff, you risk being censored or worse...

Apple is wonderful. Big Sur is great. And everything works perfectly... But I don't believe that anymore. The problem lies in the simple fact that Big Sur is too big to fit on a tiny SSD blade together with the most essential apps out there.

The feedback page is: https://www.apple.com/feedback/macos.html

Resolved.

1. Backup to TimeMachine.

2. Reset Fusion Drive and reinstall Big Sur.

　See the following link

https://support.apple.com/en-us/HT207584

3. Restore data from TimeMachine with Migration Assistant tool.

OS startup time went from over 3 minutes to about the same as Catalina's.

At present this seems to be the best solution (boot from an external SSD drive). I purchased an external USB 3.0 case (about € 10) and I put a 512 GB SATA SSD (about 65 €) into it. Now my iMac is very very fast. Only some of remarks:

1. I tried 5 different cases and some of them were slow or unstable, with frequent crashes. If you want to boot from an external drive, you need a case that insures the maximum stability.
2. The fastest external cases are based on Thunderbolt, but they are quite expensive. With a good USB 3.0 case and a cheap SSD you can achieve more than 300 MB/s write and about 400 MB/s read that is good enough for a lot of purposes
3. If your iMac supports only USB 3.0 it's not useful to buy a NVME case with a high speed SSD: a SATA case is enough to saturate the USB 3.0 bandwidth.

Let's use some logic to see who is correct and who is not.

1. There are iMacs out there that have SSD blades of 24GB, there are others (like mine) that have 28GB, and some that have 32 or even 128GB of SSD "fastness" in the 1 or 2 TB Fusion Drive "miracle".
2. For those of us who have anything less than a 32GB SSD blade, upgrading (from Catalina), installing from scratch, or re-installing does not change anything to the unacceptably looooooooooooooooong boot times of up to 3 minutes and more! A PC from the late 1980s loading Windows 3.1 did better...
3. If we go to Disk Utility and check how much space is being eaten up by some kind of disk image that is now being used as a restore point or upgrade point or whatever, on the SSD blade of the Fusion Drive, it says more than 15GB (!). The installer package of Big Sur alone is over 12 GB, meaning that once the OS in fully installed, it will be even bigger.
4. So, third-party apps and caches and frequently used chunks of data (like photo or video or music libraries) that the OS would like to load on SSD blades of anything less than 32GB, make it impossible to have the OS reside permanently on that same SSD blade. Therefore, it is residing on the much slower part of the Fusion Drive: the HDD...
5. When I start my not-even-one-year-old iMac 2019 5K 1TB Fusion Drive with 40 GB of RAM, it takes 3 (three!) minutes before I can start any app. That's how long it takes to boot, to login, to load the desktop and the Finder, and some items on the desktop. During those full three minutes I hear the HDD work very hard, which proves that I am right about the OS residing on the HDD, whilst it should be on the SSD. During boot, login, etc the system is copying the whole OS from the HDD to the SSD, and only after I have started up a number of apps, it starts looking at what apps and data should be copied from the HDD onto the SSD.

So, no... Big Sur does not have "plenty of space" on a 24 or 28 GB SSD blade. And it could be that when more apps are being installed, even a 32GB one would be insufficient.

THAT, in my humble expertise of 35 years in hardware and software, is a DESIGN FLAW of the OS. Catalina started up on my system in 30 seconds or so. I would understand that a bigger Big Sur (what's in a name...?) would add ten seconds or so, but 2 and a half minutes???!!!

No, there aren't any launch daemons or launch agents or login items or hardware causing this. It is the OS. And it is FLAWED.

And, finally, to say that the solution (!) for Fusion Drive iMacs that are as good as new, is to add an external SSD to boot from in a reasonable amount of time, is like saying that to start a car's engine, you need a couple of people pushing it. I'd call that "solution" an expensive and cumbersome work-around, and totally unworthy of the inheritance of Steve Jobs.

Let's use some logic. After all, that's what software is based on.

1. Macs on Mojave or Catalina booted up in 10 to 20 seconds. Those Macs were already running things "what users install on their systems" (your words) or (in my words) 3rd party software. That software was not causing any trouble on Mojave nor on Catalina.
2. Upgrading from Mojave or Catalina makes those same Macs boot in 4 to 5 minutes - a problem that was already reported on the official Apple developers and beta forum last Summer.
3. It is as logical and correct to claim that Big Sur is the cause of the unbearably slow boot times as it is to claim that the cause is 3rd party software that was causing absolutely no problems under Mojave or Catalina. In fact, it is clear that Big Sur is INCOMPATIBLE with 1TB Fusion Drive Macs that feature an SSD blade of 24 or 32 GB. Big Sur is so "big" that it has no way of loading itself and the most essential apps from the SSD. It has to do that from the HDD part of the Fusion Drive.

1. If the boot time of your system running once again on Sierra (or is it High Sierra?) is abnormally long, I suspect that during the upgrade - reinstall - downgrade etc. procedures, your Fusion Drive could have been split up in its two physical parts: the SSD blade and the HDD. Have you checked that? There are other threads on this forum that explain how you can check it.
2. I also suspect that replacing the HDD part of your Fusion Drive with an SSD, will make your iMac very, very fast, in boot and during normal use, even under Big Sur. As far as I understand the procedure by Apple, the original SSD blade will not be replaced and will actually keep its same function in combination with the new SSD, thus forming an SSD Fusion Drive. But this doesn't really matter to you as a user, it's a technical detail.
3. As a consumer you have consumer rights. If (a big IF) replacing the HDD with an SSD would not solve the problem, you don't have to pay anything. Just tell them that you want an absolute 100% guarantee that their solution will work, so that if it doesn't, you can get your money back. Especially because you already spent a lot of money on the RAM upgrade, which of course did not solve the problem...

I'm sorry, but you misunderstood what I said about "replacing your Fusion Drive with an SSD". I never said it would not make your Mac start up and work much faster. What I have tried to explain to you, twice already, is that in fact, your "Fusion Drive" is NOT replaced at all. Only the HDD part of it is replaced, by an SSD. The result is that you now have two SSD's making up the "Fusion Drive" instead of the previous situation with one SSD (a so-called SSD blade, a mere 32 GB in size) and one HDD. It's a misnomer to say the "Fusion Drive" has been replaced by one single SSD, but I admit a lot of people are making this mistake.

If you could do me a favour, so you will see that I am right (unless Apple has changed its approach about "replacing the Fusion Drive"):

1. Start up "System Information" (it's inside the Utilities folder of your Applications).
2. Check the sections under Hardware, entitled "NVMExpress" and "SATA/SATA Express". If the first section lists an Apple SSD, and the second one lists another SSD, then I'm right.

Of course, we could all spend a lot of money - again - and do what you have done: Have an SSD installed instead of the HDD. I don't think Apple replaced yours for free... If they did, I'd gladly hear you confirm it. And if yes, is it the same size as your previous HDD?

Thank you very much, Fabio_V, for sharing this information. I think what you say about the executables makes sense.

I have a few questions for you. Would you be so kind as to answer them?

1. How did you install Big Sur to achieve this more reasonable boot time (upgrade from Catalina? clean install?)
2. What version of Big Sur are you on (11.2.3)?
3. You say "52 seconds from login screen". I suppose you mean "52 seconds from startup chime to login screen" or am I missing something?
4. How many seconds does it take, after login, to reach a responsive desktop and responsive applications?
5. Do you have Apple apps such as iMovie, Pages, Numbers, Keynote installed?

1. I installed Big Sur from scratch.
2. 11.2.3
3. the login screen appears 7 seconds after pushing the power button. Then, after typing the password, it takes about 52 seconds to get the desktop. I've FileVault on.
4. The most used applications (in my case Safari and Mail) are quite responsive just after the desktop rendering is completed, but they're not as fast as when booting from the external SSD, of course.
5. I've Office suite, not Apple applications

BTW: I try to keep my booting process as clean as possible. After installing something, I usually remove the autolaunch components, if they're not stricty necessary.

Here I'm talking about the booting time only. Starting the biggest applications always takes some time (many seconds ot tenths of seconds). It's clear that Fusion drive is an outdated technology, but my iMac is still usable and considering it's a six years old hardware, I assume I have to accept it. Just booting from a cheap external SSD (12 € enclosure + 60 € 512 GB SSD), makes everything much faster (but not the booting process, because the recognition of the external drive at the beginning takes some more time).

Unfortunately I don't notice any major differences:

• boot to login screen: 1min
• login screen to desktop: 2min10 (with OneDrive launching automatically)
• Launching Outlook: 1min 40 (54 icon bounces!!!)
• Launching Safari: 50s
• Launching Mail: 45s

maybe I need to give it more time. We're only the end of April... ;-)

Thank you, Fabio.

Several months ago, I also was able to get a proper boot time installing Big Sur from scratch (clean install). However, as soon as I started installing apps like Pages, Numbers, Keynote, and iMovie, the boot time went up again to almost two minutes. It seemed to me that, adding apps and/or data to the Fusion Drive, made Big Sur move essential parts of the boot system to the HDD part of the Fusion Drive. I never had any slowdowns once Big Sur had taken the time to boot and to load the OS and the desktop. After about four minutes every app started up and worked fine. But the boot times stayed the same, in between 3 and 4 minutes.

So, until now, to me that is nothing new, that installing Big Sur from scratch allows it to boot in about forty seconds or so, from Apple icon to desktop.

However, several important questions remain in order to be able what is the right procedure to follow to achieve normal boot times:

1. If I understand you well, today, you installed the update of 11.3 over an existing Big Sur version (11.2.x)? Or did you, once again, do a clean install from scratch and then re-installed all your apps and restored your data?
2. How did you restore your original account if you did a clean install today? Using Setup Assistant or did you create a new account?
3. In case you used Setup Assistant, did you restore everything from a Time Machine Backup or from another backup or clone?
4. In case you created a new account, did you re-install everything manually (basically moving the apps and data from your previous account to a new account)?

Again, to make myself clear, I once also managed to get Big Sur boot in a normal time frame, but only before re-installing my apps from scratch. So it's very important to know as clearly as possible how you restored your apps and data in case you re-installed Big Sur 11.3 again from scratch.

Whether the positive result you are having now, is due to the new 11.3 version or to the fact that you left the system idle for one hour, we cannot know at this moment. But it's very important to me and many of us to know exactly how you re-installed your apps today, or if you simply installed 11.3 over an existing Big Sur system that was booting extremely slowly until now.

OK, I understood better now. I will try to summarise the steps you took, from the moment you installed the previous version of Big Sur some time ago with no improvement of boot times, up until today's version 11.3, which you installed over the previous one, using an external SSD, preserving the account(s), apps, and data.

1. Clean install of Big Sur (a version from before 11.3).
2. Manually re-install of apps and data.
3. Partial improvement of boot times, apparently because of allowing the system to be idle for 30 minutes or more after installation.
4. Today's installation of Big Sur 11.3 was done from an external bootable drive with the new version on it (macOS Big Sur Installer), not reinstalling from scratch but simply overwriting the previous version of Big Sur and thus preserving apps and data.
5. Boot times are now down to what can be considered normal (under one minute or less).

Am I correct in what I wrote above? And have you restarted your iMac a couple of times since you installed 11.3 earlier today?