Improper Volume Resizing May Cause Data Loss on Your Mac

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When it comes to resizing one or more volumes on the internal hard drive of your Mac, it is obvious for you to think at least twice before putting your hands on it. You must have a commercial partition manager compatible with the OS X version your Mac machine is running on, in case you want the process to finish successfully. Moreover, a bit expertise in drive partitioning will be advantageous not only for you, but also for the data stored on the drive. As rightly said, “Use right tool for the right job,” I would recommend using commercial partition manager for carrying out any partitioning task with your Mac OS X. However, prior to attempting partitioning, do a thorough study of the tool that you have in hand.


With the required knowledge or expertise, you feel an ease while performing the job and do it in an efficient manner. As far as hard drive partitioning is concerned, I would say take experts’ help if you are not confident enough to do the job for the sake of your data. Besides, I recommend backing up your crucial files before beginning with the partitioning task. Otherwise, you may come lose your data due to carelessness or lack of experience.

Since several data recovery software are available for different platforms, you can recover through Mac based recovery software. However, please ensure that the recovery software is commercial and you know how to use it to recover lost data.

Mac OS X includes Disk Utility that is able to fix many disk related issues, such as hard drive formatting, partitioning, repairing, erasing, imaging, and cloning. In fact, many users prefer Disk Utility to perform disk management tasks, as it minimizes the cost of partitioning to zero. On the other hand, many users do not prefer Disk Utility for disk management tasks, as they find it difficult to use. So I would say the choice is all yours whether you go for Disk Utility or a commercial partition manager for your Mac.

I, though, would discuss the steps to resize the volumes on the internal hard drive of your Mac in a secure manner. However, it is up to you if you prefer following them or simply jump to the Mac partition manager.

Resize Partitions on Mac using Disk Utility

Though partitioning the internal hard drive of your Mac is not at all an issue to worry about, it may cause data loss if you fail to perform the job efficiently. It usually happens due to carelessness or lack of experience. In order to resize the volumes on your Mac efficiently with Disk Utility, follow the steps mentioned below:

“Tip: In case you need to resize the volumes on the hard drive installed on your Mac, you can do it using Disk Utility; or else, using a commercial Mac partition manager. However, make sure your Mac is an Intel-based Mac to be able to resize existing volumes. To execute each step carefully (i.e. without data loss), I would say boot your Mac from a secondary bootable media, which can be a Bootable DVD or the Recovery HD.”

  1. After booting from the available bootable media, launch Disk Utility and highlight the hard drive shown at the top (usually above the volume Macintosh HD) in the left pane.
  2. With the hard drive selected, click the Partition tab in the right pane.

Important: Disk Utility does not show the free space on the hard drive, even though it is available. Thus, you have to resize one or more of the existing volumes to create a new or enlarge the required partition.

  1. In the Partition tab, you see a graphical view of the hard drive that is split into the volumes available on your Mac.

Important: The blue color in a volume represents data, whilst the white color represents the free space. You can resize a volume to the limit of free space in it. I recommend do not try to shrink a volume more than the free space in it.

  1. In case your Mac drive has only one volume (i.e. Macintosh HD) and you want to split it into multiple ones, you do not have to resize it, as you can directly choose the number of partitions in the Volume Scheme drop down menu.
  2. To enlarge the Mac boot volume, hold it from the bottom right corner and drag downwards. This will enlarge the boot volume and shrink the volume below it.

Important: If there is only one volume and you shrink it using Disk Utility, the space freed up is wasted.

Once you are done resizing the required volume, click the Apply button to save them. It may take a while to save the modified volumes based on the size as well as data in the volumes. Exit Disk Utility and restart your Mac normally. Eject the Bootable DVD when the Mac is booting, if inserted to boot from it.

Using Mac Partition Manager

Since the partition managers are specialized tools and designed for the disk-partitioning task, they usually are easy to work with. However, the one you choose for your Mac, make sure it has a user-friendly interface. With this requirement satisfied, you can start resizing the right partition in a manner as discussed below:

  1. Go to Applications and run the partition manager
  2. Select the hard drive or the target volume and look for the resizing option
  3. Save the volumes after you are done resizing it
  4. Exit the tool

The aforementioned steps are general that any partition manager will require you to follow. However, these steps may vary with the partition manager. Thus, “use the right tool for the right job”, as recommended.

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