slow boot from external drive

Is FileVault enabled? It’s turned on by default in Tahoe. Modern Macs have hardware-supported encryption/decryption for internal storage, but if your OS is on an external drive the decryption will be (relatively) much slower.

Another solution to your problem:

Is to run macOS and App's on the Mac mini's faster internal drive, then move your Doc's, Files and larger Photos, Music, Movie Libraries to an external drive.

Move your Photos library to save space on your Mac - Apple Support

Change where your music files are stored on Mac - Apple Support

Move your iMovie for Mac library - Apple Support

Free up storage space on Mac - Apple Support

It is a Samsung 2TB 990 Pro SSD with read/write speeds of up to 7000 MB/s, connected to the Mac mini M4 via a 40 Gb/s Thunderbolt interface, delivering an actual sustained write/read speed of around 2800 MB/s. As mentioned earlier, before the macOS update, the startup time from the external SSD was within 1 minute. However, after the update, the startup time has increased significantly to over 5 minutes.

Based on the startup logs, it appears that the system is verifying an old system snapshot on the external SSD during the boot process. This suggests that the macOS update may have left behind an old OS archive on the external SSD, which is likely the root cause of the slow startup issue.

There is no noticeable performance degradation during normal operation. The system runs smoothly once booted. However, the slow startup issue remains unresolved...

What external drive are you using…?

What items are set to startup at login…?

What else have you tried besides reinstalling…?

Next time the external drive is slow, try Safe Mode followed by a Normal startup.

see > Start up your Mac in safe mode - Apple Support

The solution there is to buy a Mac with sufficient internal storage for your needs. IMO, it’s fine to store data externally but Macs are designed to run macOS on the internal drive.

Supported isn’t the same recommended. Apple ‘supports’ disabling security protections and allowing downloaded malware to be installed. Apple ‘supports’ pasting scripts into Terminal that are offered up by malicious websites. That doesn’t mean doing those things are good ideas.

The external drive can have a large impact on how an external booting system works in addition to any other drives that you may have connected. The performance can also be problematic when using DIY enclosure/SSD combos.

So, as @den.thed has asked, what external drive are you using.

KKWho wrote:

Same issue here.

Mac mini M4 booting from a fast external SSD.After upgrading to macOS Tahoe, startup time increased dramatically — from under 1 minute to over 3 minutes, including a 2-minute black screen before the login window.

FileVault is off.

Logs show the system is booting from an OS update snapshot (com.apple.os.update-...) on the external SSD, taking about 131 seconds to verify and mount (matched the 2mins black screen). Tried deleting the snapshot (even in Recovery Mode with authenticated root disabled), but it failed.

Would appreciate any advice or a fix.

What do you mean by a "fast external SSD"?

FWIW, I use an OWC 1M2 1TB USB4 SSD (which is nearly as fast as the internal SSD) as an external boot drive with my M4 MacBook Air and times are in the range of 15-30 seconds from power on to login screen.

As I believe I have stated earlier in this thread, external booting can be very fussy about what sort of drive is used to boot from.

Also, what versions of macOS are on the internal and external drives as that can also be an issue depending on how different they are.

Same issue here.

Mac mini M4 booting from a fast external SSD.After upgrading to macOS Tahoe, startup time increased dramatically — from under 1 minute to over 3 minutes, including a 2-minute black screen before the login window.

FileVault is off.

Logs show the system is booting from an OS update snapshot (com.apple.os.update-...) on the external SSD, taking about 131 seconds to verify and mount (matched the 2mins black screen). Tried deleting the snapshot (even in Recovery Mode with authenticated root disabled), but it failed.

Would appreciate any advice or a fix.

iPhoneSE16Dream wrote:

I have Mac mini M4 with 16GB RAM and 256GB drive

Those machines are only suitable for kiosk-style applications where only a single app is ever running, such as a check-in station at a hospital or a directory lookup at an office building. The hard drive is simply too small for any other use.

etresoft wrote:

Those machines are only suitable for kiosk-style applications where only a single app is ever running, such as a check-in station at a hospital or a directory lookup at an office building. The hard drive is simply too small for any other use.

I think that’s a rather harsh characterization. Sure, I have 2 TB in my MBP and the other 5 Macs in the house have 512 GB (3) or 1 TB (2). But looking at the actual usage of my wife and kids’ Macs, they range from 65 GB to 200 GB, and they all have multiple apps installed (MS365, some have Photoshop CC, games, etc.), photos, etc.

I personally wouldn’t buy a Mac today with less than 512 GB, but I wouldn’t say 256 GB is going to be limiting for everyone. Especially with a desktop machine where a fast, multi-TB external SSD can be used for data storage.

iPhoneSE16Dream wrote:

256GB is not enough but that's beside the point as OS does offer the solution and work arounds such as installing large apps on external drive, move user home dir to external drive or even install OS on external drive , however it fails to live up to promise of delivering the solution.

Does it really promise that? There are perfectly valid and reasonable reasons to buy a 256 GB drive. But it's really not appropriate for most users.