About Unallocated Space Of Clone and Migration Operations

August 13, 2020

This post will tell something about the unallocated space that is required when you use AOMEI Partition Assistant to clone partition or migrate OS.

When will you see the Unallocated Space message?

When you use AOMEI Partition Assistant, some operations require that there must be some unallocated space on the destination hard drive. In general, there are two operations that require an unallocated space:

Clone Partition: It is function that copy data and files from one partition to another location. In the process of operating, this wizard requires the destination location must be unallocated disk space.

Unallocated Partition Clone

Migrate OS to SSD or HDD: It is the function that transfers/clones system drive to from an old HDD to a new SSD or HDD. And the destination SSD or HDD must have unallocated disk space.

Unallocated Space Os Migration

How to create unallocated space in Windows 10/8/7?

In many computers, all space will be allocated to partitions. Hence, how to split an unallocated space out of existing partitions? AOMEI Partition Assistant professional will help you solve this problem. It allows you to shrink or delete a partition to generate unallocated space in Windows 10, 8, 7. Here are the steps in detail.

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Way 1: Shrink A Partition

If a partition on disk has free (unused) space, you can use Resize Partition to shrink partition, and then the free space on the partition will become unallocated space. Right-click any partition (here take D partition for example) which has free space, and select "Resize Partition".

Resize Partition

A pop-up window will appear, and drag slider bar leftwards. Then, you can click "OK".

Drag To Left To Shrink

Now you can find that there is an unallocated disk space behind the partition D. To save the change, please click "Apply".

Apply Resize Shrink

Way 2: Delete A Partition

Deleting a partition can also create unallocated space. However, before deleting a partition, please remember to backup data or transfer files on the partition to other locations. The operation of deleting partition is very simple.

Right-click the partition (here take E partition for example) that you want to delete and select "Delete Partition".

Delete Partition

In the pop-up window, there are two ways available to delete the partition. To save your time, please tick the option "Delete partition quickly" and click "OK".

Delete Efi Quickly

Now you can find that partition E changes into unallocated space. To save the change, please click "Apply".


Good to know

How to clone data to unallocated space on an HDD or SSD in Windows 10, 8, 7? The size of the unallocated space is one of the most important considerations. There are two methods to clone partition or hard drive, which you can choose according to the unallocated space on the cloned drive.

Clone Partition Quickly: only copy the used space of the partition, and supports to resize partition during the copy process (Recommend). If you choose this method, the unallocated space could be smaller than the partition but MUST be larger than the used space of source partition.

Disk Clone Method

Sector by Sector Clone: copy all sectors of the partition to another disk, no matter it is used or not. If you choose this method, please make sure the unallocated space is equal or larger than the source partition.