Glacially slow startup

[richmond62]

So: my "new-fer-you" 2015 Retina 27" iMac (which I have had since September) is being absolutely glacial at startup and for about another 15-20 minutes . . . which as "not very nice".

MacOS 12.7.3 8GB RAM

Has anyone any bright ideas?

 

[Ben J.]

First thought: failing internal drive.

Any way you could try booting from an external drive?
You could boot from recovery (press alt at startup) use Disk Utilities to clone your internal to an external, and if the external boots fine, continue to boot from it until you can get the internal replaced.

Does booting in safe mode help? (Press shift at startup)

If it's only a problem with the boot time and it works like it should after a while, you could simply stop shutting it down, and just set the display to sleep after a period of inactivity. I keep my mac running 24/7.

But you should seriously diagnose that drive the best you can. Start with Disk Utilities.

What kind of drive is it? The original 'Fusion Drive'?

Anyway, you should back up that disk, if it's not already backed up.

 

[Bigwaff]

So: my "new-fer-you" 2015 Retina 27" iMac (which I have had since September) is being absolutely glacial at startup and for about another 15-20 minutes

Typical symptom of a failing Fusion Drive (an SSD+HDD combo). Could be the SSD failing. Could be the HDD failing.

Your options are -

1. Split your Fusion Drive. Install and boot macOS from the internal HDD and restore from backup. If you are still experiencing issues, the HDD could be failing.
   
   

   To split or not to split your Mac’s Fusion Drive

   In a recent post, I wrote about upgrading the original (failing) blade SSD in my iMac to a bigger and faster NVMe module. During that upgrade process, I wondered whether splitting my Mac’s Fu…

   raoulpop.com
2. Replace the internal Fusion Drive (the SSD+HDD combo) w/ a single larger capacity internal SSD (or HDD, but SSD recommended). Install macOS and restore from backup.
   
   

   SSD Upgrades for Apple iMac 27-Inch Late 2013 - 2019

   Get all the tools needed to safely upgrade your iMac hard drive to a new HD or SSD. Up to 8x the capacity and 92x faster than the original factory drive.

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3. Install and boot macOS from an external USB3 SSD and restore from backup. This is the easiest solution.