How can I backup data from a case-sensitive volume to a NON-case-sensitive volume?

Question

The case-sensitive volume in this instance being a desktop-mounted disk image volume.
A tragi-comedy in too many acts and hours
Dramatis Personae:
Macintosh HD: 27" iMac 3.06GHz Intel Core 2 Duo (iMac10,1), 12 GB RAM, 1 TB SATA internal drive
TB1: 1 TB USB external drive
TB2: 2 TB USB to Serial-ATA bridge external drive
Terabyte: a .dmg disk image and resulting desktop volume of the same name (sorry, I don't know the technical term for a .dmg that's been opened, de-compressed and mounted -- evanescently -- on the desktop)
Drive Genius 3 v3.1 (3100.39.63)/64-bit
Apple Disk Utility Version 11.5.2 (298.4)
Sunday morning (05/08/11), disk utility Drive Genius 3's drive monitoring system, Drive Pulse, reported a single bad block on an external USB2.0 1TB drive, telling me all data would be lost and my head would explode if I didn't fix this immediately. So I figured I'd offload the roughly 300 GB of data from TB1 to TB2 (which was nearly empty), with the intention of reinitializing TB 1 to remap the bad block and then move all its data BACK from TB 2. When I opened TB1's window in the Finder and tried to do a straight "Select All" and drag all items from TB1 to TB2, I got this error message:
"The volume has the wrong case sensitivity for a backup."
The error message didn't tell me WHICH volume had "the wrong case sensitivity for a backup," and believe me, or believe me not, this was the first time I'd ever heard that there WAS such a thing as "case sensitivity" for a drive. I tried dragging and dropping some individual folders -- some of them quite large, in the 40GB range -- from TB1 to TB2 without any problem whatsoever, but the majority of the items were the usual few-hundred-MB stuff that seems to proliferate on drives like empty Dunkin' Donuts coffee cups on the floor of my car, and I didn't relish the idea of spending an afternoon dragging and dropping dribs and drabs of 300GB worth of stuff from one drive to another.
Being essentially a simple-minded soul, I had what I thought was the bright idea that I could get around the problem by making a .dmg disk image file of the whole drive, stashing it on TB2, repairing and re-initializing TB1, and then decompressing the disk image I'd made of TB1, and doing the "drag and drop" of all the files in resulting desktop volume to TB1. So I made the .dmg of TB1, called "Terabyte," stashed that .dmg on TB2 (no error messages this time), re-initialized and then rebooted the iMac from my original Snow Leopard 10.6.1 disks and used Disk Utility to erase and initialize TB1 -- making sure that it was NOT initialized as case-sensitive, and installed a minimal system on TB1 from the same boot. Then I updated that 10.6.1 system to 10.6.7 with System Update, and checked to see that Disk Utility reported all THREE drives -- internal, 1TB, and 2TB -- as Mac OS Extended (Journaled), and no "case sensitive" BS. I also used Drive Genius 3's "information" function for more detailed info on all three drives. Except for the usual differing mount points, connection methods, and S.M.A.R.T. status (only the Macintosh HD internal, SATA 1TB drive supports S.M.A.R.T.), everything seemed to be oojah-***-spiff, all three drives showing the same Partition Map Types: GPT (GUID Partition Table.) Smooth sailing from here on out, I thought.
Bzzzzt! Wrong!
When I opened the Terabyte .dmg and its desktop volume mounted, I tried the old lazy man's "Select All" and drag all items from the desktop-mounted drive "Terabyte" to TB1, I got the error message:
"The volume has the wrong case sensitivity for a backup."
I then spent the next three hours on the phone with AppleCare (kids -- when you buy a Mac ANYTHING, cough up the money for AppleCare. Period.), finally reaching a very pleasant senior tech something-or-other in beautiful, rainy Portland, OR. Together we went through everything I had done, tried a few suggestions she offerred, and, at the end of three hours, BOTH of us were stumped. At least I didn't feel quite as abysmally stupid as I did at the beginning of the process, but that was all the joy I had gotten after two solid days of gnawing at this problem -- and I mean SOLID; I'm retired, and spend probably 12 hours a day, EVERY day, at the keyboard, working on various projects.
The AppleCare senior tech lady and I parted with mutual expressions of esteem, and I sat here, slowly grinding my teeth.
Then I tried something I don't know why I was so obtuse as to not have thought of before: I opened Apple's Disk Utility and checked the desktop-mounted volume Terabyte (Mount Point: /Volumes/Terabyte), the resulting volume from opening and uncompressing the .dmg "Terabyte".
Disk Utility reported: "Format : Mac OS Extended (Case-sensitive)." Doh!
Obviously, TB1, the 1 TB USB external drive I'd actually bought as part of a bundle from MacMall when I bought my 27" iMac, and which I had initialized the first day I had the iMac up and running (late November 2009), had somehow gotten initialized as a Case-sensitive drive. How, I don't know, but I suspect the jerk behind the keyboard. Whatever the case, when I created the Terabyte disk image (the drive's original name: when I erased and re-initialized it -- see above -- I renamed it "1TB" for quick identification), the original drive's "Case-sensitive" format was encoded too. So when I tried to drag and drop EVERYTHING from the desktop-mounted volume "Terabyte" to the newly initialized and "blessed" (now THERE's a term from the past!), the system recognized it as an attempt as a total volume backup, and hit me with "The volume [the desktop-mounted volume "Terabyte" -- BB] has the wrong case sensitivity for a backup." And, of course, the reinitialized TB1 was now correctly formatted as NOT "case-sensitive."
Well, that solved the mystery (BTW, Disk Utility identified the unopened Terabyte.dmg as an "Apple UDIF read-only compressed {zlib}, which is why the .dmg file could be copied to ANY volume, case sensitive or not), but it didn't help me with my problem of having to manually move all that data from the desktop-mounted volume "Terabyte" to TB1. I tried to find a way to correct the problem at the .dmg AND opened-volume-from-.dmg level with every disk utility I had, to no avail.
Sorry for the long exposition, but others may trip over this "case-sensitive" rock in the road, and I wanted to make the case as clear as possible.
So my problem remains: other than coal shovel by coal shovel, is there any way to get all the data off this case-sensitive desktop-mounted volume "Terabyte" and onto TB1.
Not that I know whether it would made any difference or not, one of the things that got me into this situation was my inability to get "Time Machine" properly configured so it wasn't making new back-ups every (no lie) 15 minutes.
Philosophical bonus question: what's the need for this "case-sensitive," "NOT case-sensitive" option for disk initialization?
As always, thanks for any help.
Bart Brown

Answer 1

"Am I to understand that you have a case-sensitive volume with data that you want to copy to a case-insensitive volume? And the Finder won't let you do it? If that's what the problem is, the reason should be obvious: on the source volume, you may have two files in the same folder whose names differ only in case. When copying that folder to the target volume, it's not clear what the Finder should do."
Yes, I understand all that... NOW.
What I had (have) is a USB external 1TB drive (henceforth known as "Terabyte") that I bought with my 27" iMac. I formatted, and put a minimal (to make it bootable) system on Terabyte the same day back in late November 2009 that I set up my 27" iMac. Somehow -- I don't know how -- Terabyte got initialized as "case-sensitive." I didn't even know at the time that there WAS such a thing as "case-sensitive" or "NOT case-sensitive" format.
Sunday morning (05/08/11), Drive Pulse, a toolbar-resident utility (that's Part of Drive Genius 3) that monitors internal and external drives for physical, problems, volume consistency problems, and volume fragmentation, reported a single bad block on the volume Terabyte, advising me that it would be best if I re-formatted Terabyte ASAP. I thought I could open Terabyte in a Finder window, Select All, and drag everything on the drive to ANOTHER USB external drive of 2 TB capacity (henceforth known as TB2). When I tried to do that, I got an error message:
"The volume has the wrong case sensitivity for a backup."
First I'd heard of "case sensitivity" -- I'm not too bright, as you seem to have realized.
Oddly enough (to me), I could move huge chunks of data, including a folder of 40GB, from Terabyte to TB2 with no problem.
Then the scenario unfolded per my too-convoluted message: several hours of trying things on my own, including making a .dmg of Terabyte (henceforth to be known as Terabyte.dmg) -- which left me with the exact same problem as described in the previous 4 paragraphs; and my 3 hours on the phone with AppleCare, who at least explained this case-sensitive business, but, after some shot-in-the-dark brainstorming -- tough to do with only one brain, and THAT on the OTHER end of the line --  the very pleasant AppleCare rep and I ended up equally perplexed and clueless as to how to get around the fact that a .dmg of a case-sensitive volume, while not case-sensitive in its "image" form (Terabyte.dmg), and thus able be transferred to TB1 or TB2 with no problems whatsoever, when opened -- either by double-clicking or opening in Disk Utility -- produced a desktop-mounted volume (henceforth known as the volume "Terabyte," the original name of the case-sensitive volume from which TB1.dmg had been made) that had the same case-sensitivity as the original from which it was made.
In the meantime, having gotten the data I needed to save off the physical USB "case-sensitive" volume Terabyte in the form of Terabyte.dmg, I erased and re-initialized the physical USB "case-sensitive" volume Terabyte, getting rif of the case sensitivity, and renaming it TB1. But it all left me back at square one, EXCEPT I had saved my data from the original "Terabyte" drive, and reformatted that drive to a NON- case-sensitive data now named TB1. The confusion here stems from the fact that problem case-sensitive drive, from which I made Terabyte.dmg, was originally named "Terabyte". When I re-initialized it as a NON case-sensitive drive, I renamed it TB1. I'm sorry about the confusing nomenclature, which I've tried to improve upon from my original message -- usual text-communication problem: the writer knows what he has in mind, but the reader can only go by what's written.
So, anyway, I still have the same problem, the desktop-mounted volume "Terabyte" still cannot be transferred in one whole chunk to either my internal drive, TB1, TB2, as the Finder interprets it as a volume backup (which it is), and reads the desktop-mounted volume "Terabyte" as case-sensitive, as the original volume -- from which the disk image Terabyte.dmg was made -- had been at the time I made it. 
"As long as that situation doesn't arise, you should be able to make the copy with a tool that's less fastidious than the Finder, such as cp or rsync."
I'm afraid I have no idea what "cp or rsync" are. I'd be happy to be educated. That's why I came here.
Bart Brown
Message was edited by: Bartbrn
Just trying to unmuddy the water a bit,,,