time machine file too large

iMac 10.7

My Time Machine file is filling the 500gb disk, and I need to transfer to a bigger disk. But on trying to transfer, the system said "preparing for transfer" and counted through 16 million files, and had still not stopped 'preparing to transfer' after 24 hours, so I stopped at that point. Poor disk was going to wear out. How can I do a simpler, quicker disk-to-disk transfer?

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As an aside, I found a neat trick I did not know about. I accidentally transferred the TM file to trash. Big ooops. So I transferred it back to disk using the usual drag and drop method, and it started coping the 16 million files back to disk, as in the paragraph above !! I thought the TM file was stuck in the trash forever.

However, I did not realise that the trash icon in the trash folder works in reverse. Normally it sends individual files or folders to trash. But when they are in the trash, it sends them out of trash and back to the folder they came from. Hurrah. With one click the file was back on the disk where it came from in a millisecond, with no copying necessary. Pheeew!

But I still have the problem with transfering the Time Machine file to a new disk. Do I have to start again, with a new backup system?

Ralph