09-16-2010, 10:05 AM

I have a 20" imac running Snow leopard. For months, my itunes media has been on an external firewire 250GB drive, without any problems taking up only about 90GB of space.
Suddenly, for no apparent reason, the computer reads the same drive as now only having 137GB... that's drive size, not free space.
After rescuing my files, I've reformatted the drive, repartitioned it and run both Disk warrior and Techtool as well as disk utility. I've repaired permisions, run fsck and tried the drive in several different caddies, both firewire and usb. Every program reads the drive as 137GB.
I have also now tried other drives and they are also being under-read for GB size.... 160GB reads as 127GB and so on... except that the ones that are supposed to be 120GB claim to be 122.38GB
I have unplugged everything and left it for an hour before replugging. I have tried the jumpers on all the different possibilities.
I have one more piece of information which is even more puzzling.. I have just tried one of the 250Gb drives and, when it shows on the desktop I "get info" and it tells me that the capacity is 137GB. I then opened Disk Warrior and it reads the drive as being 127GB in size.
I can't think of anything else to do... before hurling the drives through the nearest window.
any ideas anyone?

09-16-2010, 08:04 PM

Try running the Apple Hardware Test on your iMac. It's possible that the hard drive controller is malfunctioning. Even if it's not, there almost has to be some kind of hardware problem with your machine to have those kinds of errors.

See the following LINK.

Also, try attaching those drives you tested on another machine. Preferably a Windows machine. Let's see what happens.

09-17-2010, 12:55 AM

I tried the drives on a different imac.. they still register undersize. Also, my main usb external still registers correctly.. but the other dirves - even when connected through USB - still only show to be about half the size.

09-17-2010, 10:11 PM

OK, the mystery deepens... If the drives are not registering their correct sizes on more than one Mac, we can assume the problem is with the drives not the computers. That's why I asked if you could test the drives on a PC to see what happens.

It's possible that the drives were partitioned and have unpartitioned space left over but Disk Utility should show the full size of the drives regardless. Off hand I'd say you have a couple of defective drives.

09-18-2010, 02:08 AM

yeah - that's the conclusion I've come to myself... ah well... thanks anyway. get yourself an Angelo's on me.