Starting Fresh w/ ext Time Machine Disk

If you clear the TM data, you won't have a backup (unless you consider your old machine's drive the backup).

You can use Disk Utility to erase the TM drive. When it remounts, TM should automatically ask if you want to use it for backups.

If you do want to keep the current TM backup on the TM drive, you can create a second partition (using Disk Utility) and shrink the original partition to 250-300GB. Then, you can tell TM to use the new 700-750GB partition (it'll probably ask if you want to use it anyway).

Sounds like all you need to do is select the volume containing your TM backup and erase it with Disk Utility (select the volume, then click on the erase tab). Keep the format "Mac OS Extended (journaled)". It won't affect the partition with your wife's backup.

I don't think you have to worry about an old drive. The Mac file system is fine with millions of files on a single partition - something that will easily happen with a couple of years of TM backups (especially if you have swapped drives and then continued with the same backup timeline). Even my internal drive has 1.5M files in the 313GB used. My TM backup drive has over 13M and dates back to 2011 (taking up around 1TB).

Time Machine is fairly unique, but it's rules aren't too complex. It uses a hidden database of changed files on the source drive. Then, it either writes a complete version of the new file, or maintains a hard link to an existing one in the backup set. If you manually went and perused one of the TM backups, you would see what looks like a complete copy of your entire source drive in each backup, when in fact, you're seeing mostly hard links (only 4KB). Btw, it's not recommend to do any Finder operations on a TM backup. You need to use the TM interface.

If you want to read up on the gory details, I believe ArsTechnica has a good write up in its review of OS X 10.5 Leopard.

Enjoy your new iMac!

garycurtis said:

I was warned about not using Finder operations in a Time Machine drive. Although I frequently do a 'drag and drop' of a file or folder FROM Time Machine to my hard drive.

This because I'm frightened off by that RESTORE command on Time Machine. It looks to me like an Outer Space movie — with all the visual effects. Boy, Steve Jobs probably got real energized when he saw that function at work.

Thanks for your detailed explanation. In a month I'll be getting a new 2012 iMac and will upgrade to OS Mountain Lion. Time to get the Missing Manual so I can learn that OS. And, since I'll be taking a few classes at the Apple Store, I can ask questions about TM and the Mountain Lion features.

My wife has a new MBP with OS 10.7 or 10.8. It creeps me out that you can see Preference of Library Files. It's a sign that I need to learn more.

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Doing a drag & drop from the TM backup seems to result in the actual file being copied in ML. I seem to remember issues back in 10.5, but I never tried restoring the file that way. The problem was that if you dragged the file, you would get the hard-link - which is a file in its own right (4KB) - instead of the actual file.

Don't fear the restore (almost a song title ). After you tell it to restore the file/folder, the system will exit the TM space-flight interface and return you to the normal Finder (or app, if you are restoring from within and app, for example TextEdit or iWorks apps - if you're in the app and launch TM, you will have the same interface as ML "browse all versions" (from the title bar)). When you are back in the Finder, you are given the option of restoring to a different location, replacing the original, or keeping both versions.

The nice thing about using the TM "space" interface is browsing versions. If you click on the "go-back-in-time" arrow, TM will automatically flip past folders until it sees something has changed - either modified, or detecting a that deleted file returning to the folder (I've probably used the "find that deleted file" feature most often). And, as I mentioned above, it works for individual file types from with their app.

The reason (I believe) TM has such a radically different display is to make sure it is differentiated from the normal OS X GUI.

I think you're talking about the fact that your user Library folder is hidden from the Finder > Go menu or Finder window side bar. If you hold down "opt" when clicking on the Go menu, you will see your Library folder is once again listed. While you have that [~/Library] window open, you can drag the folder icon from the title bar to the Finder window side bar and always have access to the Library folder from there.

garycurtis said:

I got the last point about revealing the Library folder when it is hidden in OS 10.6 or newer.

The rest of what you said largely goes over my head. I don't understand some of the acronyms. What is ML, for one.

The solution for me to to get a lot smarter about the MAC OS. I will have someone in the know give me a demo of the restore function in TM.

When I spoke about plucking an individual file or folder from the backup database on my TM drive, I am usually referring to a photo. A JPEG or a Tiff. Just a single item which I then drag across from the LaCie TM partition to my hard drive. Call me a Neanderthal. I'll be buying my new iMac from the local Apple Store. So I have no excuse not to take their free classes on applications and Mountain Lion.

I appreciate your input and am printing out this thread.

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Glad to help. Sorry - ML = Mountain Lion

To get a better explanation on Time Machine and hard-links, Ars Technica has that great in-depth review of 10.5, and Wikipedia should have some info too.

Anyway, all that aside, you don't need to know how Time Machine does its thing. Just let it do its thing and use the "space" interface to find that deleted or old version of your file. I only brought up some of the behind-the-scenes stuff since you were bypassing the "space" interface.