I know you cannot use DiskWarrior to rebuild the Mojave directory on an internal drive. I am able to Carbon Copy clone an external drive (in my case, an SD card) from my Mojave system and I can use DiskWarrior to rebuild the directory of the external drive.

I asked DiskWarrior tech help if cloning the external drive back to the internal drive would be the same as a directory repair. They said:

"Cloning a disk does not make a directory repair. It simply makes a new directory. This may solve some problems, but not all."

So, until the next major iteration of DW is able to cope with APFS drives, this is better than nothing. I guess.

I've been using DiskWarrior and TechTool Pro since OS 8.5. Can't get out of the habit, but maybe Carbon Copy Cloner is all I really need now.

Although not as powerful as DW or TTP, Disk Utility is still a viable option. It fixed a problem for me that I had had with my APFS internal disk.

Thanks. I always run Disk Utility before and after any other utility, be it DiskWarrior, TTP, Carbon Copy Cloner or OnyX – part of my OCD rain dance. In my defense, I've never had a problem. I'm sure that has more to do with OS's since Snow Leopard than my computer skills.

It seems to me the DW tech person did not fully understand your question. You said you cloned, repaired with DW, then cloned back. Would the cloned back directory still have the repairs? Why not? The tech only said cloning fixes some problems, not all. You cloned and repaired.

Don't confuse the various functions performed by DW (DiskWarrior), TTP (TechTool Pro), DG (Drive Genius), and DU (Disk Utility).

DU, TTP, and DG already cope with APFS drives as well as they are ever likely to. (I don't know for sure about DW but I strongly suspect it is the same.) They all can do Volume REPAIR which, as indicated by the Disk Warrior tech involves creating a new volume directory. The volume directory is a LOGICAL structure that is written on top of the physical structure. What these utilities cannot do is OPTIMIZE the physical layout of the volume or files in APFS by placing files in contiguous sectors to speed access on HDs. Any location on a Solid State Drive can be accessed directly so any such optimization would be pointless and in fact could potentially to shorten the life of the drive itself. Since APFS is optimized for use on SSDs those optimization functions do not make sense and are not available[//u] in the various disk utilities and never will be on APFS formatted volumes whether on an HD or SSD.

Repairing/Rebulding the volume directory will not and cannot repair errors in FILE structure or data contained in files and while any write operation could trigger the drive recognize a bad sector and remap it to a spare (if a spare sector is available), it cannot directly identify or even infer that media on the drive surface is flaking off much less repair or stop further deterioration. In fact you can perform Volume Repair on a drive that is technically in a failed status. Media flaking off of the surface of a drive is the most common type of HD failure and tdentifying that failure is the reason for performing a Surface Scan to identify if there are bad data sectors which is a good indicator of impending drive failure.

[u]NOTE: There are standard S.M.A.R.T. parameters for HDs such as reallocated sector count and Reallocation event count which do the same thing, but to the best of my knwkedge, TTP is the only utility that reports S.M.A.R.T. in that detail. For SSDs the equivalent would be Available spares and Percentage Remaining (again AFIK only available through TTP).

The present version of Disk Warrior cannot repair APFS volumes. Read Alsoft's explanation