It appears that, under Mac OS X 10.5.6, Disk Utility seems to have a few quirks, namely a glitch in which it does not properly format some drives. Many users have attached both external and internal drives to their macs, and have not been able to build an OS X volume on the drive.
There are a couple of legitimate reasons why Disk Utility could fail to create a partition or format a drive. The primary reason is if the disk is failing. If the drive has physical errors or a glitch in the firmware, it will not be able to complete commands given to it by the system and will cause a variety of errors. In these cases the drive may create repetitive clicking or grinding noises. While most drives have "S.M.A.R.T" reporting that can notify the system of hardware failures, on firewire and USB drives this technology is not supported. Additionally, if there was a hardware failure, users would not be able to access the drive and format at all; but in many instances users are reporting the ability to format drives only in one format.
David Schwartzer writes:
"Disk Utility will format [my] drive as a Master Boot Record and FAT32 or as a Apple Partition Map and Free Space drive but not a Mac OS X Extended. I even tried using Drive Genius but I get error messages saying the formatter failed." In these cases, the drive is clearly not failing, since they can be accessed just fine in the formats that will work. Additionally, many users are finding that their drives which cannot be formatted in a system running later versions of 10.5, can be formatted if mounted and managed on a system running 10.4.
Matt Bogen adds:
"I had the same problem...My G5 running X.5.6 would not format, partition, or erase...I tried both FW-400 and FW-800 connections; same result. I have another G5, same model, running X.4.11, and I tried it on there; it formatted and partitioned immediately."
This situation has been reported by other users running 10.5.6, as well as some users running 10.5.5, which indicates there is a problem with how Disk Utility is handling the drives. As such, if users are running 10.5 and cannot format a drive, it is recommended to first try the drive in another non-Leopard system (Windows, or Tiger) to see if the drive will format. Hardware failures are always a possibility, but users can ensure they will not throw out a perfectly good drive if they try another system. While users can try various third-party disk utilities to manage their drives, many times these solutions use built-in drive managing technologies for formatting, and therefore may run into the same errors as Disk Utility. Hopefully the problems in Disk Utility that are preventing disks from being recognized will be addressed by Apple in a future update.