View Full Version : What's the right way to set up a new backup or replacement drive?

09-13-2009, 09:42 AM
Note: Apple has produced an article that goes into detail about how to do this with recent OS versions. You'll find the article here:


For older OS versions (pre-10.11), the following should help beyond what Apple has provided.

It's very important to properly initialize a drive if you want to be able to use it as a startup drive - whether it's a new backup drive or a new internal drive.

Most drives come set up for Windows, and while they'll generally work with the Mac, they won't work properly as startup drives.

A "partition scheme" is the low-level on-drive stricture that is used by the OS to find the "volumes" (the "drives" that appear in Finder—a physical disk can have one or more) on a physical disk. There are three different "partition schemes" that can be used on the Mac:

Master Boot Record—this is the partitioning scheme used by Windows, and how most drives are shipped.
Apple Partition Map—the original partitioning scheme used by the Mac, required for Power PC based Macs.
GUID (aka GPT)—the new partitioning scheme used by Intel Macs.

So, here's what you should do with a new drive.

Note: partitioning normally erases a drive. If you have a drive that's using the wrong partition scheme, iPartition, from Coriolis Systems, can change the partition scheme without deleting the data, and can also repartition drives with data in place.

Start Disk Utility (it's in /Applications/Utilities)
Select the external drive hardware in the sidebar.
You must select the drive hardware, above any existing volumes, or the Partition tab will not appear.
Click the Partition tab
Use Disk Utility's controls to divide the drive as needed, even as a single large partition. Use "Mac OS Extended (Journaled)" as the format type and name appropriately
Click the Options button
Choose the proper partition scheme (GUID for Intel macs, Apple Partition Map for Power PC) and accept the page
Click Partition.

That's all there is to it!