External HD reformat interrupted; now I can't use disk

Question

I recently purchased a 2TB Seagate GoFlex external hard drive (connected to my Airport Extreme via ethernet cable) to use at a Time Machine backup. After setting it up per the Seagate instructions, the initial backup was agonizingly slow - just 200 GB in 36 hours. Other discussion topics recommended reformatting the drive using the Partition tab in Disk Utility, making sure the Partition Map Scheme was set to either Apple Partition Map or GUID Partition Table. However, when doing that, the process hung at "waiting for disks to reappear." I accidentally closed out of Disk Utilities, and now I cannot access the disk to complete or re-do the process.
The disk only shows up in Disk Utility if I open up Time Machine and tell it to "Back Up Now", but the backup fails because the disk is unavailable. If I then select the disk in Disk Utilities then select Partition, all selections are grayed out. Any suggestions?

Answer 1

Turn off Time Machine by first setting the backup device to None. Next:
Drive Preparation
1. Open Disk Utility in your Utilities folder.
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Cick on the Partition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID (for Intel Macs) or APM (for PPC Macs) then click on the OK button. Click on the Partition button and wait until the process has completed.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.
Bear in mind that backing up over a network is slow. Even using Gigabit Ethernet the best throughput you will achieve is that of a USB drive which is slower than Firewire 400. 200 GBs in 36 hours sounds about right. However, once the initial backup is done the incremental backups will not take as much time. To avoid the time needed for the initial backup it's advisable to do it by direct connection to the computer's USB or Firewire port rather than over the network.
Message was edited by: Kappy