Backing up and restore Mac OS partition: trickier than I expected

After the disaster I had today, I learned the lesson and start taking more time to backup and double check the Mac OSX partition before doing anything crazy. 

Here's a few lesson I learned:

- Don't create a image of your partition while you are running on that partition.  Interestingly enough, Disk Utility actually allows you to do so, but when you run a check on that image, it will fail like hell eventually.  So just make sure that you create and restore Image by booting up the OS installation disc, and then use the Disk Utility.

- I tried to restore a boot partition, but got an error saying "Restore Failure: Could not restore - Cannot allocate memory" at the VERY END of the restore process.   And then I realized that in my setting I am copy data from ONE harddisk in a dual slot harddisk bay to ANOTHER harddik in another slot of the harddisk bay.  So I thought, maybe that's the problem.  So I tried restoring the first partition from the image file in the second partition of the same harddisk.

- Sometime booting back to MacOS from Windows can be tricky.  I experineced a few times when the Mac Mini kept booting to Windows 7 even though I explictly select boot to Mac OS.  Solution?  Well, I shutdown the external hardisk, shutdown the machine, start up again, in Win7 go to BootCamp utiltiy, set start to MacOSX, and work again.  Odd.

- I know that remove drive letter from HFS drives should NOT cause any problem, but I did experience something odd that the partition used to work on Mac suddenly failed.  So I better do some backup before doing such an action.  (Well, honestly, I think I probably made other mistakes that cause problem instead of just take away drive letter).

- Remember to REMOVE dropbox on the BASE OSX (on the MacMini internal harddisk).  Otherwise it may confuse dropbox when switching between the BASE OSX and the daily use one in the external harddisk.