External Hard disk has space problem for Time Machine

Question

Im not sure this is the right place to post this, but I've just got OSX.5 so Time Machine is new to me. I've got a 500Gb Firewire Lacie Drive which I now have, as far as I can see, about 110GB of stuff in. I have a bout 300Gb to back up. Currently my mac can only see 260GB free, which means theres about 150GB that isnt explained. I have run Disk Inventory, which shows the dot files on the drive. There seem to be hardly any. Is there anything else that could be taking up such a large amount of disk space? Theres one movie file of 28GB that I cannot move off the drive.

Answer 1

Tim Whelan2 wrote:
Im not sure this is the right place to post this, but I've just got OSX.5 so Time Machine is new to me. I've got a 500Gb Firewire Lacie Drive which I now have, as far as I can see, about 110GB of stuff in.
Let's see what Disk Utility (in your Applications/Utilities folder) says. When it starts, click the top line for your drive in the sidebar (should have size and make), then the Partition tab. Towards the bottom is a *Total Capacity* line, followed by two different numbers: one in GB, the other in bytes. The first will be about 465 GB, the second roughly 500 billion. This is the different way of counting: decimal vs. binary.
There's also a *Partition Map Scheme* line. This should be followed by GUID or +Apple Partition Map.+ If your drive isn't one of those, you're going to have a problem using it with Time Machine. Report back what this says.
In the center part of the display is a diagram showing all the partitions currently on the disk. Each is represented by a box, with a name in the center, and the amount used represented by light blue shading.
If there's only one partition, it's total size and amount available will be in the center, shown in GB.
If there are 2 or more, click each one in turn to see it's sizes. The Total of the sizes should be almost the same as the total at the bottom (the Partition Map takes a bit of space).
It sounds like you may have 2 partitions, one for TM backups, one for your "other stuff". If so, each partition is treated separately for most purposes: there should be two icons on your desktop and/or Finder sidebar, for example.
Report back what you find, and whether it makes sense to you or not. Then we can figure out what's going on and what you need to do.
But note this: This drive is a bit small to use with Time Machine. TM works best if it has 2-3 times the space of what it's backing-up, so it can keep a few months of your backups. See item #1 of the Frequently Asked Questions post at the top of this forum.
Even if you could use the entire 465 GB or so, that's less than twice the 300 gb you want to back up. That would work, for a while, but depending on how you use your Mac, TM may not be able to keep your backups for very long.