Bugs in Windows Disk Management tool

For partitioning of MBR and GPT disks, Windows provides a Disk Management tool and the command line tool diskpart. While the Disk Management tool is easy to handle, it comes with a few bugs, that can cause serious trouble. Here are issues I came across during the years.


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Wrong results shown for GPT disks

Inspecting a gpt partitioned disks (default on UEFI systems) using Windows disk manager won’t give you appropriate results. Here is a screenshot I’ve obtained from one of my systems.

Have a look at the upper right corner. The columns Free Space and % Free reports wrong values on several partitions. The Recovery Partition, the EFI System Partition, the OEM Partition and also the Recovery Partition are reported as 100 % free – which isn’t the case. So Windows Disk Management is pretty useless to check, if the Recovery Partition on UEFI systems is filled. This is required, if Windows 10 installing reports “We couldn’t update system reserved partition” (see KB3086249).

Partitioning scheme on MBR disks may be reported wrong

Recently I stumbled upon another case, where Windows Disk Management may cause serious trouble, if a user misinterpret a partitioning scheme, reported for MBR disks. The case has been mentioned within this (German) forum. The disk layout reported from Windows Disk Management for a extended partition containing a Linux partition was presse wrong. The Windows command line tool diskpart reports the following (correct) disk partition structure.

DISKPART>  list part 
 
  Partition ###   Type              Size    Offset 
  -------------  ----------------  -------  ------- 
  Partition 1    Primary              40 GB  1024 KB 
  Partition 2    Primary             40 GB    40 GB 
  Partition 3    Primary              40 GB    80 GB 
  Partition 0    Extended          113 GB   120 GB 
  Partition 4    Logical             40 GB   120 GB 
  Partition 5    Logical             40 GB   160 GB 
  Partition 6    Logical             29 GB   200 GB 
  Partition 7    Logical           4095 MB   229 GB

Take note of extended partition 0. This partition should contain all logical drives listed above via diskpart. Below is the partition structure shown in Windows Disk Management (unfortunately only in German).


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The MBR base disk contains 3 primary partitions, so a fourth primary partition or secondary partition (extended partition) is left (MBR may contain only four partitions). An extended partition may contain several logical volumes. Windows Disk Management reports the two partitions for Windows 10 and for data as an extended partition (the green frame). The Linux partitions 5 and 6 are shown as primary partitions – so the MBR disk seem to contain 6 primary partitions (which is impossible). Changing the partition structure bears the risk that the disk will be left in a corrupted state or the Linux installation will be non bootable anymore.

The MBR dynamic disk trap

There is another trap where non experienced users may landing during re-partitioning a MBR disk. As mentioned above, a MBR disk may contain only four partitions at all. Here is a screenshot from a disk structure shown in (German) Windows Disk Management.

It’s a typical structure of a OEM disk. If a users decides, to split the partition containing logical drive C: to separate data from the Windows install disk, it’s not possible (no free partition left).

But Windows Disk Management allows to shrink an existing primary partition, to create free unallocated space on the disk. Then the unallocated free disk space may be right clicked, and the user can choose the context menu command Create new simple volume.

A wizard will guide the user trough the steps to create the new partition. Windows Disk Management will create a dynamic disk that is shown in the screenshot below.

Although Windows will boot from a dynamic disk, this partition structure may cause serious trouble using third party disk tools, installing multi boot environments or accessing the dynamic disk. So my recommendation is to use either diskpart or a third party partition tool to alter disk partition structures.

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