Resizing Time Machine Backup Volume

Question

As a recent iMac purchaser, I started using Time Machine with an external 1TB FW400 drive about a week ago. All is working well (as far as I know) but I now wish that I had partitioned the external drive e.g., 800GB for Time Machine and 200GB for another volume.
1) Is there a way for me to resize (make smaller) the TM partition such that I don't lose the TM backup files already on it? Current backupdb is 90GB, free space is roughly 900GB (part of which I'd like to use to create a small partition). If so, how?
2) Alternatively, if the creation of a second partition from some of the unused space on the existing TM partition will result in loss of data on the TM volume, is there a way for me to first copy the TM data into a folder on my iMac internal hard drive (250GB free)? And, if so, how should I restore the backupdb from the folder back into the TM volume when I'm done repartitioning the external drive?
I've tried copying the backupdb two ways, with no success. 1) After turning off Time Machine, a "copy" of the database seemed to be working okay but eventually failed with message "The operation can't be completed because the selection contains both backup items and non-backup items." 2) I had also tried a sudo find . -print | cpio -pdmv /Users/somedir in the hope that I force a total copy using Unix utilities, but received plenty of error messages. (I guess there's more to the backupdb than just a collection of files.)
Since I only recently started using TM, I'm okay with scratching what I have and starting over, but I'd like to determine if there's a way I can solve this problem the hard way... .
Thanks.
P.S. If I need to scratch the existing TM volume and start over (after creating two partitions on my external drive), are there any gotchas I need to be aware of before (re)starting TM on the new partition?

Answer 1

Yes, you can do what you want. I would make a backup of your TM backup as a precaution, but it isn't a necessity. To backup the TM volume you will need another drive large enough for the space used by the TM backup. You must use the Restore option of Disk Utility to essentially clone the volume to another drive.
To resize the drive do the following:
1. Open Disk Utility and select the drive entry (mfgr.'s ID and size) from the left side list.
2. Click on the Partition tab in the DU main window. You should see the graphical sizing window showing the existing partition. A portion will appear as a blue rectangle representing the used space on the drive.
3. In the lower right corner of the sizing window is a resizing gadget. Select it with the mouse and move the bottom of the rectangle upwards until you have reduced the existing partition enough to create the desired new volume's size. The bottom of the sizing window will appear gray. Click on the Apply button and wait until the process has completed.
4. Click on the [+] button below the sizing window to add a new partition in the gray space you freed up. Give the new volume a name, if you wish, then click on the Apply button. Wait for the process has completed.
You should now have a second volume on the drive.