Learn how to reconfigure the disk mirror of your Windows system if it needs to be rebuilt due to corruption or disk failure.
On a Windows system, data redundancy is achieved by mirroring the primary disk to a second one. This is similar to a RAID 1 configuration but only involves two disks.
Requirements
- A Windows dedicated server with a software mirror
- Administrative access to the server via RDP
Instructions
Establish a remote desktop (RDP) connection to your server.
Once logged in, right-click on the Start Menu button and open Run.
Enter "cmd" and click on OK.
The method to use depends on the partition style of your disks. Follow the instructions below for MBR or skip to the subsequent section for GPT. If you are unsure, run diskpart at the command prompt and enter list disk. Check the "Gpt" column in the output.
Rebuilding the mirror (MBR partition scheme)
At the command prompt, open DiskPart:
C:\Windows\system32> diskpart
Listing all disks and volumes
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 447 GB 0 B *
Disk 1 Online 447 GB 447 GB
Disk M0 Missing 0 B 0 B *
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Mirror 447 GB Failed Rd System
In this example, Disk 1 is a replacement drive that has been installed to replace the defective Disk M0 which had been physically removed previously.
Removing the replaced disk from the configuration
DISKPART> select volume c
Volume 0 is the selected volume.
DISKPART> break disk M0 nokeep
DiskPart successfully broke the mirror volume.
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Simple 447 GB Healthy System
DISKPART> select disk m0
Disk M0 is now the selected disk.
DISKPART> delete disk
DiskPart successfully deleted the missing disk.
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---s
Disk 0 Online 447 GB 0 B *
Disk 1 Online 447 GB 447 GB
Initializing the replacement disk
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> convert mbr
DiskPart successfully converted the selected disk to MBR format.
DISKPART> convert dynamic
DiskPart successfully converted the selected disk to dynamic format.
Recreating the mirror between the first and the second disk
DISKPART> select volume c
Volume 0 is the selected volume.
DISKPART> add disk 1
DiskPart succeeded in adding a mirror to the volume.
<===>
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
* Disk 0 Online 447 GB 0 B *
Disk 1 Online 447 GB 0 B *
Repeat this step for each existing volume from Disk 0 that you want to mirror on Disk 1, using the associated drive letter (i.e. d, e, f, etc.).
The volume state will be Rebuild during the process, which may take several hours depending on the data stored on the disk. You can check the status in DiskPart:
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 0 C Windows NTFS Mirror 447 GB Rebuild System
It is best not to restart the server until the rebuild process is complete.
Rebuilding the mirror (GPT partition scheme)
At the command prompt, open DiskPart:
C:\Windows\system32> diskpart
Listing all disks and volumes
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 1863 GB 0 B * *
Disk 1 Online 1863 GB 1863 GB
Disk M0 Missing 0 B 0 B *
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Mirror 1862 GB Failed Rd Boot
Volume 1 EFI FAT32 Partition 350 MB Healthy System
In this example, Disk 1 is a replacement drive that has been installed to replace the defective Disk M0 which had been physically removed previously.
Removing the replaced disk from the configuration
DISKPART> select volume c
Volume 0 is the selected volume.
DISKPART> break disk M0 nokeep
DiskPart successfully broke the mirror volume.
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Simple 1862 GB Healthy Boot
Volume 1 EFI FAT32 Partition 350 MB Healthy System
DISKPART> select disk M0
Disk M0 is now the selected disk.
DISKPART> delete disk
DiskPart successfully deleted the missing disk.
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 1863 GB 0 B * *
Disk 1 Online 1863 GB 1863 GB
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Simple 1862 GB Healthy Boot
Volume 1 EFI FAT32 Partition 350 MB Healthy System
Initializing the replacement disk
On the new disk, create default and mandatory partitions, reflecting the existing partitioning of the first disk:
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> clean
DiskPart succeeded in cleaning the disk.
DISKPART> convert gpt
DiskPart successfully converted the selected disk to GPT format.
DISKPART> select partition 1
Partition 1 is now the selected partition.
DISKPART> delete partition override
DiskPart successfully deleted the selected partition.
DISKPART> create partition efi size=350
DiskPart succeeded in creating the specified partition.
DISKPART> format quick fs=fat32 label=EFI
100 percent completed
DiskPart successfully formatted the volume.
DiskPart successfully formatted the volume.
DISKPART> assign letter=t
DiskPart successfully assigned the drive letter or mount point.
DISKPART> create partition msr size=128
DiskPart succeeded in creating the specified partition.
DISKPART> list partition
Partition ### Type Size Offset
------------- ---------------- ------- -------
Partition 1 System 350 MB 1024 KB
* Partition 2 Reserved 128 MB 351 MB
Recreating the mirror between the first and the second disk
DISKPART> select volume c
Volume 0 is the selected volume.
DISKPART> add disk 1
DiskPart succeeded in adding a mirror to the volume.
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
* Disk 0 Online 1863 GB 0 B * *
Disk 1 Online 1863 GB 0 B * *
Repeat this step for each existing volume from Disk 0 that you want to mirror on Disk 1, using the associated drive letter (i.e. d, e, f, etc.).
Recreating the boot environment and setting boot options for the second disk
DISKPART> select disk 0
Disk 0 is now the selected disk.
DISKPART> list partition
Partition ### Type Size Offset
------------- ---------------- ------- -------
Partition 1 System 350 MB 1024 KB
Partition 2 Dynamic Reserved 1024 KB 351 MB
Partition 3 Reserved 127 MB 352 MB
Partition 4 Dynamic Data 1862 GB 479 MB
Partition 5 Dynamic Data 71 KB 1863 GB
DISKPART> select partition 1
Partition 1 is now the selected partition.
DISKPART> assign letter=s
DiskPart successfully assigned the drive letter or mount point.
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Mirror 1862 GB Rebuild Boot
* Volume 1 S EFI FAT32 Partition 350 MB Healthy System
Volume 2 T EFI FAT32 Partition 350 MB Healthy Hidden
DISKPART> exit
Leaving DiskPart...
Back at the command prompt, copy the boot files from the boot (EFI) partition on the first disk (Disk 0) to the boot partition on the second disk (Disk 1).
Type the following three commands and execute each one with Enter:
robocopy s:\ t:\ * /e /copyall /xf BCD.* /xd "System Volume Information"
bcdedit /export t:\EFI\Microsoft\Boot\BCD
bcdedit /store t:\EFI\Microsoft\Boot\BCD /set {bootmgr} device partition=t:
Then launch DiskPart again and run the following commands:
DISKPART> select volume s
Volume 2 is the selected volume.
DISKPART> remove
DiskPart successfully removed the drive letter or mount point.
DISKPART> select volume t
Volume 1 is the selected volume.
DISKPART> remove
DiskPart successfully removed the drive letter or mount point.
The volume state will be Rebuild during the process, which may take several hours depending on the data stored on the disk. You can check the status in DiskPart:
DISKPART> list volume
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C Windows NTFS Mirror 1862 GB Rebuild Boot
Volume 1 EFI FAT32 Partition 350 MB Healthy Hidden
Volume 2 EFI FAT32 Partition 350 MB Healthy System
It is best not to restart the server until the rebuild process is complete.
Go further
For more information and tutorials, please see our other Dedicated Servers support guides or explore the guides for other OVHcloud products and services.