Why is SD! taking so long?
 

I had disconnected my "main" SD! backup drive while I was attempting to resolve the problem I was having with my smaller SD! "secondary" backup drive. The last scheduled backup to that "main" SD! drive was 2 days ago.

I reconnected the "main" drive, and manually initiated an SD! backup, and it is still running after many hours, instead of the typical 20 minutes or less it usually takes. Looking at the progress window, it appears that SD! is going through every file and backing each up as if all had changed since the last time it backed up to that drive.

Is it normal for SD! to do this, even though only a small handful of files have actually changed since the last backup?

That depends on what really changed, what happened to the drive, etc. We're only going to recopy files that are really different.

Maybe I'm misinterpreting ...currently it says:

"1,994,882 of 2,497,470 files evaluated, 1,991, 268 files copied."

and

"344.82 GB evaluated, 0.00 MB already up to date, 339.83 GB copied."

That certainly looks like everything was copied. But, again, I have no way to know what's really going on here - just that it's copying because something is different. Perhaps your drives fell off? Is the space on your internal drive going down?

Don't know what you mean by "fell off."

It's a 1 TB drive, with 430 GB available. My internal is 1 TB with (you guessed it) 430 GB available.

Oh s**t!! I'm an idiot...I manually backed up to my 2 TB TM drive!

I mean "fell off the bus". Ah, backing up the wrong thing would certainly do it.

Should I quit now, or let it finish and then run a TM backup followed by an SD! backup to the correct drives?

Probably should stop it, if you don't want the backup there.

I don't recall: What happens if TM kicks in and begins to create a backup to a drive with files on it (i.e., to the drive which has been overwritten with my SD! backup)? There's enough room for all of the files, but would it create a problem later on? (IOW, should I reinitiallize this particular drive to get rid of the SD! backup, and then start TM backups anew?)

If you're using Smart Update, SD! won't touch the TM backups. It'll put the SD! backup side by side with it.

Ah! So TM and SD! can live side-by-side on the same drive, right?

OK. What happens when TM needs more space? Will it delete only the older TM files, and leave the SD! copy alone? (And what if it were reversed: If SD! needed more space, would it wipe existing TM files? It's not an issue here in the near term, inasmuch as the drive has a capacity of 2 TB, and my internal's capacity is 1 TB...just a general question.)

Yes, see the FAQ about this (Help > Frequently Asked Questions). TM will grow and grow until it fills the drive - you're better off with a partition...

My plan is to do the SD! backup to the correct drive, then erase the one just completed to the TM drive, bringing the TM drive back to its original state.

Question: Can I delete the SD! backup by deleting the folders it created on the TM drive, and do so via the Finder?

To delete the SD! backup, I'd create an empty source image, then use "Backup - all files" with "Smart Update" to copy from that image's volume (disk) to the Time Machine drive. That'll leave the TM backups alone, and remove everything else.