How to enlarge a partition on an external hard drive

Question

I backup with Time Machine to an external hard drive.  It is currently configured into two partitions, one being used to backup and the second used for other purposes.  I have maxed out the backup partition and wish to expand its size by eliminating the second partition.  Disk Utility allows the elimination of the second partition, but when I attempt to enlarge the backup partition to include the now unused space on the disk I get the following message:
Partition Failed
Partition failed with the error:
Filesystem resize support required, such as HFS+
with journaling enabled.
What does this message mean and how can I accomplish my goal?
Thanks.

Answer 1

I know this issue is 14 months old, but perhaps someone else will read it in the future. I ran into this problem of needing to resize an external drive and discovered that Mac's Disk Utility program, built into the Mac OS, allows you to do this without losing data or needing to buy additional software.
Here's how:
1. Open Disk Utility and select the root diretory of the external disk you want to resize. (If the disk is partitioned, it will have a subdirectory for each partition.)
2. At the top of the dialog box, select Partition.
> You should see five buttons across the top of the dialog box: First Aid, Erase, Partition, RAID, and Restor
> If you select a subdirectory, rather than the root directory, the Partition option is not displayed, because you can't partition a subdirectory.
3. On the screen you should see the disk split into the different partitions. Select the partition you wish to resize.
4. That partition will be highlighed and the lower right part of the box should have a little triangle-like series of lines. Click and hold this triangle, then drag it down to make the partition larger, or drag it up to make the partition smaller.
5. When you get to the size you want, hit apply.
6. Disk Utility should do its thing and your disk will be resized.
Viola. You are finished.
Take a look at http://macs.about.com/od/applications/ss/diskutilitysize_3.htm for pictures of this process.