{"id":40377,"date":"2017-03-28T11:00:30","date_gmt":"2017-03-28T16:00:30","guid":{"rendered":"https:\/\/eshop.macsales.com\/blog\/?p=40377"},"modified":"2017-04-21T17:26:32","modified_gmt":"2017-04-21T22:26:32","slug":"partitions-101-rules-to-resizing-volumes-how-to-without-losing-data","status":"publish","type":"post","link":"https:\/\/eshop.macsales.com\/blog\/40377-partitions-101-rules-to-resizing-volumes-how-to-without-losing-data\/","title":{"rendered":"Partitions 101: Rules to Resizing Volumes & How to Without Losing Data"},"content":{"rendered":"

Disk Utility, the all-purpose tool for working with storage devices connected to the Mac, has long had the ability to create partitions and manage the resulting volumes. It has been the go-to tool for formatting a Mac’s drives, erasing data, securely wiping information, and creating multiple partitions.<\/p>\n

With the advent of OS X Leopard<\/a>, Disk Utility picked up a much-prized feature: the ability to non-destructively resize existing volumes and partitions. Before OS X Leopard, you needed to fully back up all the data on a drive if you intended to alter the drive’s partition map in any way. That’s because changing the partitions, by adding, removing, or resizing, resulted in the loss of all data on the volume.<\/p>\n

Thankfully, you can now resize a partition without losing data, provided you follow a few basic rules.<\/p>\n

Resizing was pretty straightforward with OS X Leopard through OS X Yosemite, but starting with OS X El Capitan, Disk Utility underwent a user interface makeover that altered how partitions were resized.<\/p>\n

<\/a>
(Disk Utility from older versions of the Mac OS was arguably easier to use for resizing partitions.)<\/strong><\/figcaption><\/figure>\n

We’re going to look at how to resize a partition without losing data with the new (OS X El Capitan and later) version of Disk Utility.<\/p>\n

The Rules of Resizing a Partition<\/strong>
\nDisk Utility can be used to resize existing partitions you may have on a disk, but there are some rules that govern whether you’ll be able to make the changes you envision. For the most part, the resizing capabilities in Disk Utility need some careful attention to details to ensure the results you want will occur. Be sure to pay attention to these rules.<\/p>\n

Also, it’s a good idea to have a current backup<\/a>. Although the basic idea is to resize a volume without losing data, it’s always better to play it safe. In addition, there are times when, because of the type of changes you wish to make, you’ll be forced to delete one or more partitions<\/a> to accomplish your goals; having a backup is key to a guaranteed successful completion.<\/p>\n

Resizing Rules<\/strong>
\nResizing is limited to specific disk formats. Currently, only disks formatted with the GUID Partition Map support resizing.<\/p>\n

Fusion Drives are a special case<\/a>. They’re made from two separate disks: a fast SSD<\/a> and a slower, but much larger, conventional disk drive. Apple allows a Fusion Drive to have up to two partitions; however, the SSD is never included in the second partition, which is made up only of the conventional hard drive. To add another wrinkle, partitions that are part of a Fusion Drive can’t be resized using the Disk Utility GUI, even though it’s possible (though very complicated) to resize using the Terminal core storage commands. Because of the complexity, we won’t be addressing core storage tricks, or resizing or partitioning Fusion Drives in this article.<\/p>\n

Fusion Drives and Boot Camp<\/a> are another special case. Removing a Boot Camp partition that is part of a Fusion Drive and resizing the remaining partition should be performed with the Boot Camp Assistant and not Disk Utility.<\/p>\n

Some other quick rules:<\/p>\n