Partition a Hard Drive in Mac OS X
If you want to create a new partition in Mac OS X, you won’t need to use anything fancy other than the built-in Disk Utility. Be sure to have a full backup of your hard drive before adjusting the partition table just in case something goes wrong. If you have an adequate backup, proceed:
Add a new hard drive partition in Mac OS X
- Launch Disk Utility from /Applications/Utilities/
- Select the hard disk you want to partition from the left side of the app
- Click on the “Partition” tab
- Click on the + button to add a new partition
- Specify a name for the new partition, select a filesystem type (Mac OS Extended Journaled is default), and choose a size either by manually entering a capacity or by dragging the slider bar in the partition map
- Click on “Apply” to create the new partition
You can make partitions any size as long as you have the available disk space to accommodate it, and creating the partition shouldn’t affect your existing filesystem either as long as there is free space. Nonetheless, there is always a chance something could go wrong, which is why I recommended you backup your drive first.
After you have clicked ‘Apply’ to create the new partition, it will be immediately accessible in the Finder to use how you want. A new partition will behave like a new hard drive, and it will appear on your Desktop as a new drive which can be ejected, mounted, formatted, just like a hard disk.
I partitioned my drive before installing Mac OS X Lion so that I could maintain my stable Mac OS X 10.6 system software while still exploring the Lion 10.7 Developer Preview. Another common use is to partition large external hard drives for a specific Time Machine backup partition. Time Machine will backup a drive until the available space is taken, so if you set it to backup to a partition, it will only take up that space and leave the other partition alone, allowing the drive to serve multiple uses.
Deleting a partition
Removing partitions is just as easy as creating one. All you need to do is follow the steps above to get to the partition table, select the partition you want to delete, and then click the “-” button rather than the plus icon. Remember, if you delete a partition, you will lose data that exists on it.
You need to defrag your HD before adding a new partition, especially when the HD has been in use for a while.
Not totally correct. If you have a Mac Journaled file system (as is shown in the screen-shots), there is no such thing as defrag.
Not sure you’re right about that. I had this situation a month ago. My HD (with no partitions) was/is Mac Journaled. The only way I could partition it was by first defragging. Until I tried that, I constantly got failures.
Mac OS X doesn’t need to be defraged. Plus if you own an Solid State Drive (SSD) the manufacturers highly recommend you DON’T defrag as this seriously reduces disk life.
Read Apple’s support page: http://support.apple.com/kb/ht1375
Gah why didn’t I think to partition my backup drive! It’s a hassle for me to delete them now I can just reformat the partition!
Whats the chance of screwing up your hard drive? i want to try Lion but don’t want to risk my data and lose it for the second time (first time mac got stolen).
“Whats the change of screwing up your hard drive?”
Repartitioning is one of the highest risk things you can attempt with your data. If something goes wrong, like a power failure or human error, the damage to your data will be catastrophic.
So don’t do it without backing first. At least buy a cheap external USB harddisk.
I was just reinstalling 10.6 and repartitioned my harddrive. It’s important to click ‘Options…’ and select ‘GUID Partition Table’ before you apply the new volume scheme.
When I setup a Linux system it always requires that there be a partition dedicated to SWAP in the tables. I can’t find anything about this for the Mac, does this mean the Mac doesn’t use a swap partition? Or the utility takes care of all these little details automatically when you proceed with an installation?
Mac OS X handles swap itself, without a dedicated swap partition.
For some reason the + button to add a new partition is grayed out. What am i doing wrong or missing?
heres my screenshot
http://a.yfrog.com/img739/6183/fdb.png
You’re running Snow Leopard which treats the boot drive differently, you may need to boot off a DVD or USB key to partition the primary disk in that case. In OS X Lion, you can partition from the boot drive.