How to fix error when converting a basic disk to dynamic?

Wei Wang 1 Reputation point

I'm trying to add a mirror for the system disk in a Windows 2019 server. Which requires the disk be converted from "basic" to dynamic.

Using DISKPART, here is what I got:

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    System             650 MB  1024 KB
  Partition 2    OEM                100 MB   651 MB
  Partition 3    Primary           2048 MB   751 MB
  Partition 4    Reserved            16 MB  2799 MB
  Partition 5    Primary            928 GB  2815 MB

DISKPART> convert dynamic

Virtual Disk Service error:
The selected GPT formatted disk contains a partition which is not of type
'PARTITION_BASIC_DATA_GUID', and is both preceeded and followed by a partition

How do I proceed with this?

Thank you much for your help.

Edit: More specific questions:

  • What information are in the "OEM" and "Reserved" partitions? They seem to be the offending partitions.
  • If I convert them to MBR partitions and lose the data in them, would Windows still boot?
  • I used "dd for Windows" to copy the OEM and Reserved partitions to files. Is that good enough for backup those partitions?
Windows Server 2019
Windows Server 2019
A Microsoft server operating system that supports enterprise-level management, data storage, applications, and communications.
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  1. Limitless Technology 37,501 Reputation points

    Hello @Wei Wang

    The issue here is because you are trying to convert a disk/partition that contains system information.

    Be aware that converting a disk of partition to Dynamic will require to DELETE all data in that partitiion, so a backup of your information is required.

    The steps would be:

    list disk
    select disk #
    list partition
    select partition #
    convert mbr

    Hope this helps with your query,

    --If the reply is helpful, please Upvote and Accept as answer--

  2. Docs 13,091 Reputation points

    Data should be backed up whenever it is at risk.

    There is no automatic data loss when converting from basic to dynamic.

    GPT or MBR can be converted from basic to dynamic.

    This link may be useful:

    Frequently asked questions about the GUID Partitioning Table disk architecture

    What happens when a basic disk is converted to dynamic

    For a drive to be eligible for conversion to dynamic, all basic data partitions on the drive must be contiguous.

    If other unrecognized partitions separate basic data partitions, the disk cannot be converted.

    This is one of the reasons that the Microsoft Reserved Partition must be created before any basic data partitions.

    The first step in conversion is to separate a portion of the Microsoft Reserved Partition to create the configuration database partition.

    All non-bootable basic partitions are then combined into a single data container partition.

    Boot partitions are retained as separate data container partitions.

    This is analogous to conversion of primary partitions.


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