Imaging with Disk utility is slow

Disk Utility has never been good at "cloning" a macOS boot drive as it does not (or at least did not) recreate the hidden Recovery partition. It is fine for restoring some bootable .dmg images Apple has used over the years for bootable diagnostic disks, or for creating .dmg archive files for folders. I tried it years ago, went back to using CCC for its reliability.

It depends what you mean by image. While CCC is a file based app, it will create a read-only compressed .dmg "image" of the entire boot drive including the hidden recovery partition through a file copy process (at least for macOS 10.15 & earlier...CCC must utilize macOS' ASR utility to clone the APFS volume on macOS 10.11+...may no longer work for M1/M2 Apple Silicon Macs). While this is not a bit for bit image of the entire drive (used & unused blocks), it is good enough to make a backup archive of the entire OS & data being able to restore it to another drive and have it bootable. I use this method all the time on client Macs which I need to replace drives.

Or are you looking at a low level bit for bit clone of the entire drive for used & unused sections?

Edit: Is this speed issue something new or has it always been an issue? Besides a drive issue, a cable, adapter/dock/hub/enclosure could be the problem. I recently had an unusual severe performance issue using CCC to clone a system and discovered it was the Anker USB-C adapter...removed it from the equation and the clone proceeded quickly as I had expected. I had not noticed any issues with smaller transfers.

Is there another way to do this on the Mac that would be faster?

You can use a backup method that creates incremental backups rather than a complete one each time. This saves time, and reduces wear on all drives involved.

You can use Time Machine, the built-in backup feature of your Mac, to automatically back up your personal data, including apps, music, photos, email, and documents. Having a backup allows you to restore your Mac from a Time Machine backup if you ever delete your files or can't access them: Back up your Mac with Time Machine - Apple Support. However, Time Machine backups aren't bootable, i.e. you cannot use them as a recovery startup disk.

You could use Carbon Copy Cloner to create bootable backups of your Mac. You can restore individual files, or recover your entire system, just like Time Machine. To learn more, see: Carbon Copy Cloner.

Why does the Mac take 3x longer?

It's possible the Mac's aftermarket Samsung SSD could be experiencing issues. To check, you can use DriveDx.

Jack

tmpc wrote:

However, I did find something that is a bit annoying. The Mac drive image in Disc Utility is actually a partition image. So, the emergency boot partition on the original drive isn't in the disk image. I don't honestly know if there are any other hidden partitions on an OS X drive. But, the drive did boot, so I guess that's good enough.

That is why we recommend using CCC as CCC will automatically recreate the hidden recovery partition/volume. The local recovery partition/volume is necessary if you want to enable Filevault and for a faster more reliable boot into Recovery Mode since many people have problems accessing Internet Recovery Mode.

I know that CCC uses the macOS / Disk Utility ASR utility for cloning macOS 11.x+ volumes as that is the only way to clone the APFS volumes with increased security features (not a file copy). I don't know when this ASR feature was enabled for this task or how it works exactly as I've never had time to investigate since CCC does what I need to easily backup & restore a client Mac, or how to do this using just macOS. CCC only has the older style file copy for macOS 10.15 and earlier.

Another vote for Carbon Copy Cloner...

http://www.bombich.com/software/ccc.html

I know that CCC does preserve some third party software activations, but I'm sure some third party software which are more strict & controlling will lose their activation with CCC.

If you want a low level bit for bit copy, then I'm not sure what options are out there, but I know that the free open source command line utility GNU ddrescue will do that since I use that for cloning failing hard drives. The downside is there is no precompiled binary for macOS and you would need to run it from a bootable external drive. You can save the image in a raw image file, but there is no compression unless do it manually later on. I ended up either using a Linux boot disk (Knoppix does have Gnu ddrescue installed) or a Linux system to do those clones because macOS just got in the way due to the errors produced by a physically failing drive.

You can try using the command line utility "dd" which may be available from Recovery Mode (not sure since it is a very limited environment). "dd" is an older more basic & limited in function (no progress status on the macOS version and no error notifications)...should be Ok as long as the drive is healthy.

GNU ddrescue and "dd" require the source drive to have no mounted volumes when performing the clone. It is also very easy to make a mistake when restoring an image. There are some Linux utility disks out there such as Clonezilla, but I don't recall what utility it uses although it provides I believe an ncurses GUI interface.

FYI, while cloning is possible with your older Macs, keep in mind that cloning probably won't work on the newer M1/M2 Apple Silicon Macs. CCC already has noted this a couple years ago (it is a best effort now) and there have been several forum posts where people have mentioned that it is no longer possible to clone a macOS boot drive on Apple Silicon after one of Monterey's updates.

For optimal USB 3 transfers, make sure your external SSD supports UASP protocol as it changes how the data transfers are done which is more efficient than the USB 1/2 method. All devices (docks, hubs, adapters) in the chain between the computer and the UASP SSD must also support UASP. UASP also keeps the SSD transfers high when slower USB 1/2 devices are connected to the same hub/dock with UASP support, otherwise those slower devices will slow the SSD transfers.

Also, SSDs can slow down significantly during sustained writes once the SSD's write cache has been filled (many times it only takes 40 to 60 seconds). This becomes more significant with TLC SSDs and especially QLC SSDs since QLC NAND is much slower than TLC NAND. Also, the less free space on an SSD will also affect the write speeds especially since I don't believe macOS supports TRIM on external SSDs.

The USB adapters, docks, and hubs can also impact performance as these items don't always work the same between macOS, Windows, or Linux. There can be some odd compatibility issues involved. Try disconnecting all other devices when attempting to clone/image the drive or perhaps even booting into Safe Mode on the Mac which is performing the cloning/imaging to see if that makes a difference in case some other software is interfering.

There has got to be a faster way to do this.

Well, there is CCC and Time Machine. That's what I'd use. IMO, they are more useful than creating an image each time.

There'd be whoppin' big diffs in time to image depending mostly on size & sped of drive, even a WD Black 6TB 3.5" will be twice as as fast as a WD Green 1 TB 3.5", & older drives 1/4 the speed .