Very slow boot on Fusion and Big Sur

I think a clean install would help you out. The 128 GB SSD blade of your 1TB Fusion Drive is more than enough to accommodate the OS and its essential apps. My guess is that an upgrade installation of Big Sur over a previously installed OS is not always able to recognise or use the SSD blade as it should. Other users who have a 128 GB SSD, have been successful in making Big Sur load in less than half a minute, after a clean install, not an upgrade install.

Your drive is working fine, as it should be.

The structure goes Physical Storage (Fusion Drive) > Container (APFS) > Macintosh HD (System data, with snapshot) > Macintosh HD - Data (user data).

For more speed, you really need that external SSD.

If you need more help, please start a new discussion form, as this discussion form is already quite long.

Cheers,

Jack

Thanks for confirming this.

What do you mean: “more speed”? I just want my iMac to not run like it’s 1995. It would be weird to assume that the only way to accomplish this is by attaching an external disk. Something is very wrong with Big Sur, and I haven’t seen any solutions anywhere.

I don’t really see the point in starting yet another thread. I’ll just monitor the existing threads.

For the "more speed" with an external SSD, you can get read/write speeds of around 420-500 MB/s.

You do not have to do this. This is just for people who need the extra performance of an SSD.

The reason I suggested starting a new form is then we can gather an EtreCheck report from your Mac, see your exact performance numbers, and start troubleshooting yours. (Perhaps a piece of software adds to your slowdowns, etc. All cases are different.)

Cheers,

Jack

I tried that already, and as I did a clean install, the report returned nothing useful. I'll just have to accept that my iMac used to boot in 20 seconds and now takes 5 minutes. Guess I can leave it on 24/7.

exchanging the internal Fusion Drive to a 1 TB Samsung EVO SSD brought my unusable machine (iMac 27 late 2015“ back to 2021 on full speed and better performance than ever.

Forget an external solution.

I can definitely believe replacing the Fusion drive with a SSD drive will improve performance.

However, when Apple releases a new OS, performance should be similar (or slightly lower) than previous OS versions. Not like what a lot of us are seeing.

QUOTE FROM ANOTHER THREAD:

“Restart in Safe Mode - Shift _key immediately at startup. Will do a Repair Disk, clean cache files and only loaded required software to boot computer. It will take longer than normal to boot - Normal. Once logged in it will appear different than normal - Normal. Let it run this way for 5 - 8 minutes and then restart in Normal Mode... ” P. Phillips User Level 6

-> Don’t know if that particular advice from P. Phillips at Apple Support Communities actually worked or not in my case, but my Big Sour now loads MUCH faster!

Boot time with Catalina used to be almost immediate (10-15 sec), but with BS 11.2.0 and 11.2.1 ended up at an excruciating 50-60 sec. So just before upgrading to 11.2.2 earlier this week, I did as suggested above i.e. a proper ‘Safe Mode’ startup (waited 20min, so as to let the system do its cleaning job), then restarted normally - still sluggish - but right after that, I finally installed the 11.2.2 update. Now it flies: 12-15 sec. max!(?) Big Sur not Big Sour anymore ; )

Was this the beneficial effect of a deep cleanup operation as a first step, or simply an improvement implemented by Apple via its 11.2.2 installation process? Oh, and how should I approach the newest 11.2.3 version that came out 72hrs afterwards!? A bit scary ; (

(Note: my iMac is a late-2015 model with a 2.128 TB Fusion drive, so ‘Big Sour’ sluggish startup is surely not only affecting smaller fusion drives with a 24 or 32 GB SSD blade...)

In my case, a late-2015 2TB Fusion iMac, Catalina (and all previous OS) would always load in a lean 12 seconds; BS 11.0, 11.1, 11.2, and 11.2.1 would all of a sudden load in a minute i.e. 5x longer; earlier this week I was excited because the freshly installed 11.2.2 had brought back its startup time to an encouraging 15 seconds, thinking that perhaps Apple had cleaned its mess... Now, BS 11.2.3 puzzles me with its lukewarm 30 second boot. Why so much discrepancy between OS versions on the same system, and between different Mac users? 5+ minutes is actually 10x longer than before, unbelievable! Let's hope that 11.2.4 comes with a solution as soon as possible.

Finally, having spoken to people at Apple Support (here in Europe) who care and listened carefully at what I was saying in order to help them understand the problem, a Senior Apple engineer took the trouble to inform himself about what was going on with Big Sur and Fusion Drive iMacs, called me back, confirmed that there definitely is a problem that has nothing to do with hardware issues nor with any software that would not behave nicely, but indeed with the combination of Big Sur and Fusion Drives. Those of us who have small SSD blades as part of the Fusion Drive system, will indeed see bootup times of in between 4 to 5 minutes before any app becomes responsive, as described by so many users here and on the Developers forum.

What I am publishing here underneath, is what this Senior Apple engineer told me himself on the phone:

The solution: Wait for an update of Big Sur that will fix the problem. Don't waste time trying to run software that checks if all is OK. Don't waste time re-installing Big Sur. Don't waste time installing Big Sur from scratch (clean install). Nothing that has been tried to fix it in the last four months will fix it. It will have to be fixed from inside Big Sur with an update. Find and read the release notes of every update coming out from now to see if the problem was dealt with.

However: Do know that there is no guarantee that the problem can be fixed!...

This is the Apple response (finally) to our big problem.

I will post this in some other threads that deal with the same problem, as soon as I can.

Thanks for reporting back. Let’s hope they fix it soon. It’s very worrying that it took this long to at least acknowledge the issue, and even then it’s in a private call.

The fact there is no more uproar about this must mean it’s not affecting every machine with a fusion drive.

The engineer hinting that the issue might never be fixed, seems to be a real possibility. We’re already 5 months into Big Sur and Apple Silicon is the future getting all of Apple’s attention. If we want this fixed, it’s best to make sure the issue gets a lot attention.

Thanks for posting this and I am so glad I found your reply. I was driving nuts when my iMac slowed with the boot. But I noticed some apps are also slowed down like Lightroom. I have a 2017 4k 21.5 3.4Gh iMac with 1TB Fusion drive and I started to worry about all this. I guess it's all about BigSur. I guess the only solution is to wait for the upgrade or get sad inside.

It gets worse. I turned my iMac off for the weekend, and booting this morning took 12 minutes (!) before I got a responsive desktop. Even the Music app bounced for 2 minutes...

Then I got 10 push notifications stating an error with installing apps. It were iOS apps I installed on my iPhone. Obviously they can't run on my Intel iMac. What gives? Apple needs to step up its game with this macOS release. Fast.

This is the first time I am not updating all my Macs to the latest version.

Well, iMac 2017 2Tb and 128SSD -- and guess what, I am here looking for help. Same ridiculous update and start up times. Applications are unresponsive and I was too late for a meetings few times already. Have to run it 24x7 now. Have 40 GBs of RAM installed, that is the only solution to use it without pain after startup wait times. Considering to sell it for all the good and bad it has. Do not think Apple is interested in our complains. They are selling M1 computers now...

There are a number of users that own your type of iMac with the 2 TB Fusion Drive featuring the 128 GB SSD blade and have been able to make Big Sur start up in a normal way and have all apps running fine, after a clean install. Even on my 2019 iMac 1 TB featuring a 32 GB SSD blade, I have been able to make Big Sur start up in less than 30 seconds, but only after a clean install and before installing any apps (e.g. Pages, Numbers, Keynote, iMovie, Garageband). As soon as I added those Apple apps, the startup times went crazy (first over 2 minutes, and finally over 4 minutes), so I didn't even try to install 3rd party apps (e.g. Adobe Photoshop and Lightroom), and downgraded back to Catalina, which made my iMac very, very happy. Big Sur appears to have a problem with the amount of available space on the SSD blade and positioning itself and/or apps on that SSD part of the Fusion Drive or on the HDD part, during and after startup.