Migrating Your Mac OS X Installation to a New Drive

Upgrading the original drive in your Mac is a great way to improve performance and/or increase the storage capacity of your machine. When transferring user data from one drive to another, Apple generally recommends installing a fresh copy of OS X, then using Migration Assistant to bring over your user data.

This allows for a clean base to start from. As we use our computers, they tend to collect "leftover" files from installers, old applications we've erased, various logs and the like. By doing a fresh installation, then bringing over our data, we can easily clear out these "old" files and start anew — without all the leftovers — for maximum system performance and stability.

With OS X 10.7 and later, this method is nearly mandatory, as these versions of OS X feature an invisible recovery partition that is created during installation, as well as background processes that temporarily store a number of invisible files on your drive.

Nothing will put the brakes on an installation like trying to install the wrong drive. Make sure you double and triple check your computer model (you can do that in System Profiler). If you're still not 100% sure, go ahead and get in touch with one of our sales or tech representatives — they'll be happy to help ensure your upgrade drive is compatible.

In order to transfer your data, you'll need to have both your original drive and your new drive connected at the same time. For single-drive computers such as most laptops, you'll need a device to connect the old drive to your computer after your new hard drive is installed.

If you plan on using your old drive for ongoing external storage when you're done, you can use the enclosure that you will put your old drive into. In most cases, you can use a standard external enclosure for appropriately sized drives, Newer Technology Voyager Drive Docking Solution, or the Newer Technology Universal Drive Adapter to connect. In some instances, though (most notably with MacBook Air models), you'll need a special enclosure for the specialized drive used.

For those extremely rare cases where you can't connect your old drive externally (e.g., you don't have the proper enclosure), the following steps will be slightly different. See the Special Note at the end of the article for more details.

Note: If you have a Time Machine backup drive, you can also use that in place of your original drive when transferring files using Migration Assistant.

Make sure you have a current backup of your data on a separate drive before you begin upgrading. If you have a Time Machine backup already, you should be good to go. This will ensure you have a separate, non-attached copy of your data in the unlikely event of accidental data loss during the upgrade.

This one is fairly self-explanatory. If you need help installing, OWC has an extensive library of installation videos that walk you step-by-step through hard drive installation for most user-upgradable Mac models.

Note: This step is only for systems where the original drive has been removed. Systems that have both new and old drives inside the Mac can skip to Step #6.

Once you have replaced your old drive with the new one in your computer, connect your old drive to the external enclosure or adapter that you will be using, as mentioned in step 2. Connect the now-external drive to your computer using the appropriate cable and proceed to the next step.

For 10.6 or earlier, boot to your installation disc. For those running 10.7 or later, you'll want to boot to the OS X Recovery System by holding down Command-R at startup. Select the language you want to use and then proceed to the next step.

Use Disk Utility to format the new drive. In all versions of OS X you can find Disk Utility in the Utilities menu at the top; in 10.7, it's also in the main list in the center of the screen.

Once Disk Utility is open, select the new drive from the list on the left. Once you have the disk selected, click on the "Erase" tab on the right.

Set the Volume Format to "Mac OS Extended (Journaled)". This is the recommended format for all drives that have OS X installed on them. The name can be anything you want. Once you have set those two items, you can click the "Erase..." button.

Once you've formatted your drive, you can close Disk Utility. If you're in 10.7 or later, you'll need to select the "Reinstall Mac OS X" option from the Mac OS X Utilities screen. In earlier OS versions, quitting Disk Utility will take you right back into the installer.

Follow the steps as they are presented to you, making sure to select your new drive (the one you just formatted in the previous step) as the install location. The installers for Mac OS X are very straightforward to use; all you need to do is follow the on-screen instructions. Once you have filled in the required information, the actual install will begin. This can take quite a while, depending on your internet connection speed. Fortunately, the process at this point is automated, so you can do something else while waiting for the install to complete.

In most cases, there will be updates available for the OS version you just installed. Once the initial setup has completed, go to the Apple menu, select "Software Update...", and run all the updaters that are available. Restart if necessary and repeat the process until there are no more updates to install.

Once OS X has installed, your computer will restart to the new drive and walk you through the final setup steps. Continue through the on-screen prompts until it gets to the point where it asks if you'd like to import user data from another system. This part of the setup process uses Apple's built-in Migration Assistant utility. If for some reason you skip the initial setup, you can find Migration Assistant by going to your "Applications" folder, then the "Utilities" folder inside that. Once Migration Assistant is running, select the option to transfer your user information from another disk and click the "Continue" button.

The next screen will list the things you can transfer. Select any users you want to bring over to your new drive, as well as any applications and network settings. You can either select them all, or you can select/deselect items individually by expanding the folders via the disclosure triangles. There is an option for "Files and Folders," which you will likely want to bring over as well, since some applications install some settings in non-standard places.

Once you have selected the items you would like to bring over, click the "Transfer" button. Depending on how much you're transferring, this can take a while. After Migration Assistant finishes, you can continue the rest of the setup and boot to your new drive.

Note: If you're running OS X El Capitan v10.11 you can skip this step as there is no "Repair Disk Permisions" option.

Use Disk Utility (Applications > Utilities > Disk Utility) to repair permissions on your new drive. Select the new OS X volume in the list on the left, then click on the "First Aid" tab, then click on "Repair Disk Permissions".

Run all your apps and go through your files to make sure everything is working and nothing is missing. You may have to re-authorize some apps or, in very rare cases, reinstall the application altogether. Make sure everything is as you want it before continuing.

Once you've checked to make sure your data came through correctly, you're ready to go. Now you can either erase your old drive in the external enclosure and use it for other purposes or save it for posterity.