Help me understand partitioning!

When you make a new partition, you make a new "digital" hard drive. For example you can have a 500 GB HDD in real life. But have two partitions of this hard drive each 250GB (or in another way divided, like 100 and 400 or 200 and 300 and so on).

You can do this to run multiple operating systems. For example when you have one hard drive and you want to install mac os x and windows you need two different hard drives (mac os x and windows require their own hard drive, plus they use a different structure). Instead of buying a second one, you can partition your hard drive to give your mac the idea you have two. (when you want to install windows and need to partition, the boot camp guide will help you do this, so you don't need to do it before you begin).

However these days I don't see the point to use partitions only for running different operating systems.

If you want to make a partition, you'll have to open the hard drive utilities program (found in your program folder, then the "help utilities/programs", don't know the exact name). There you can choose a hard drive and choose to partition it. However this will erase your hard drive.

 

Command+Spacebar then type in Disk and it should come up with the program, Disk Utilities.

In windows we make two partitions to put the OS on one and your data on the other, so if windows blows up you can just reinstall and not worry about backing up/restoring data.

In OSX I guess you could use this for organizational purposes.

If you wanna run windows in bootcamp you have to make a second partition just for windows.

This is mainly because OSX uses it's own language for it's system, HFS+.
Windows uses FAT32 and now, NTFS.

In short, don't mess with it, there's no need unless you are messing with windows or something of that nature.

If you really want a partition:
Open Disk Utility
Click on your drive's model name
Click on partition
In the lower left of the drive image, there's a + so you can click that to make a new partition and adjust the size.

If you really wanna save the changes just click apply. But you can juse check it out and see what it would look like if you did it. So for now just close the window.

If you have another hard drive, you can change the volume scheme also and make like 30 partitions. This option is greyed out on your boot drive (it was on mine).

 

Wasted space?

 

I'm not sure what you mean about wasted space on a single-partition drive, but there is some wasted space when working with multiple partitions. Operating systems expect at least ~5 GB of free space to run happily, so with two partitions, you'd have to leave that much free on both partitions. There's also some space lost in the partitioning process itself.

I do have three partitions on my iMac's 1.5 TB hard drive, though: 160 GB for Mac OS X and my documents, 32 GB for Windows, and about 1.1 TB for my movies and games and such. I find that it's easier to have movies in /Movies (or more accurately /Volumes/Minipax/Movies) than trying to deal with everything in my home folder. It also lets me exclude that partition from my Time Machine backup, since the data on there is more or less replaceable and my backup drive is nowhere near big enough for all of that.

For the record, partitioning works in exactly the same way on Windows.