There’s a fundamental flaw in Windows 10 Setup when performing a clean install on a new empty hard disk or SSD. The same is true when wiping the disk empty on a device containing a previous Windows 10 installation and deleting all partitions and performing a clean install. The flaw is, Windows Setup positions the small but important 500 MB recovery partition first on the system disk. If and when future feature upgrades need more space to store the recovery environment, the recovery partition cannot expand, and a new recovery partition is created.
Let’s see how Windows Setup partitions a GPT disk on UEFI-based systems. When installing on an empty disk, you can just click Next and Windows Setup will partition the disk automatically, after which it proceeds with installation:
You can see how Windows Setup partitions the disk if, instead of clicking Next, you click New and accept the defaults. Windows Setup will partition the disk and show you a message that says setup will create all necessary system partitions automatically:
When you click OK, partitioning is handled, and places the recovery partition first in the resulting disk layout:
Windows will be installed. After a clean install, checking Disk Management shows you this default partitioning scheme. Here’s a sample screenshot from Disk Management showing the default Windows Setup partitioning after a clean install of Windows 10 version 1803. The recovery partition is highlighted (yellow):
Notice that the small 16 MB MSR partition between EFI and C: partitions will not be shown in Disk Management, simply because it is not and will not be formatted. This is OK, not an error or issue in your Disk Management.
Everything is OK. That is, until some new feature upgrade requires more space for its recovery partition. Because it cannot be expanded (the EFI partition blocks this), a new recovery partition is created following the Windows system partition C: by shrinking it, and creating a new recovery partition in the space left unallocated when the C: drive gets shrunk.
The Recovery Partition needs more space!
Upgrading version 1803 to version 1809, more space for the recovery environment is needed. The current recovery partition cannot expand, therefore the 1809 upgrade shrinks the C: partition and creates a new recovery partition in the freed space that follows the C: drive (blue highlight):
The original recovery partition (yellow) has become obsolete, and is neither needed nor used anymore. It can be deleted, and all partitions moved to the left. Unfortunately, this is an impossible task with Windows’ own Disk manager. To make that happen, you need a third party tool.
The Windows 10 recovery partition can do something no other partition can: it can expand backwards by shrinking the partition in front of it, and expand to fill that space. However, it can only do this if the preceding partition is the Windows partition C:. That is, the recovery partition can only expand backwards if placed immediately after the C: drive. Then, the next time a feature upgrade requires more space for the recovery partition, it will again shrink the C: drive and expand backwards to fill that space (green highlight):
What this means is that gradually, over a few years and countless in-place upgrades, your Windows drive C: will shrink a bit. That’s because the recovery partition requires a bit more space every three or four feature upgrades. The only way to avoid this is an occasional clean re-install. This, however, shouldn’t be a problem because the recovery partition will never “steal” more than a few gigabits from the C: drive.
What, a third Recovery partition?
At some point in the future, you might want shrink the C: drive and create a data partition on the freed space. This will create a new partition between C: and the current recovery partition at the end of the disk. Then, the next time an upgrade requires more space, a third recovery partition will be created between C: and your new Data partition, because the recovery partition at end of the disk can only expand backwards if it appears directly following the C: partition. In the next screenshot, the yellow highlight marks the original recovery partition in this sample clean install of 1803, and blue marks the new recovery partition after the 1809 upgrade, and green the space where a new recovery partition would be created when the current one (blue) cannot expand as needed:
How to avoid this?
Personally, I will never just boot from the Windows install media and click Next. The two or three minutes I need to plan my clean install or deployment will protect me from unexpected issues in the future. Planning the partitioning is part of this effort. I begin my clean installs with DISKPART, creating the partitions I need manually before launching Windows Setup. See this tutorial of mine at TenForums.com for some tips: DISKPART – How to Partition GPT disk
When deploying, see this Win10.guru series about how to use the Microsoft Deployment Toolkit (MDT): Windows Deployment with MDT. MDT, as with all modern Microsoft deployment tools and services, partitions the system disk correctly. That is, it places the recovery partition after the C: drive, not in the first position in the disk layout it builds.
Multiple recovery partitions are not an issue, if “messy” Disk Management does not disturb you. Windows 10 is always aware of where to find the latest, default recovery partition, and will use it when you need to access the recovery environment. This is more cosmetic, causing no problems, and does not cause any issues. It just makes the disk layout look confusing. Fix it if you, like me, like things to make sense and work well over time. Leave it alone otherwise. It’s entirely up to you!
Author: Kari Finn
A former Windows Insider MVP, Kari started in computing in the mid 80’s writing code for VAX / VMS systems. Since then, he’s worked in a variety of IT positions. He specializes in Windows image capture, customization, repair and deployment as well as Hyper-V virtualization. Kari is a proud Team Member at number #1 Windows site TenForums.com.