Create or break a mirrored boot volume

  • Article

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

 

To create or break a mirrored boot volume (Itanium-based computers only)

To ensure that your Itanium-based computer can load Windows if one of the disks or controllers fails, you can add a mirror to the boot volume, which makes an exact copy of the volume that contains the Windows operating system.

  • To create a mirrored boot volume

  • To break a mirrored boot volume

To create a mirrored boot volume

  1. Print this procedure or write down the steps before attempting to create a mirrored system or boot volume.

  2. Read and understand all of the information in the Important and Notes sections. In this procedure, disk 0 is the boot disk and disk 1 is the disk that you will mirror to the boot disk.

  3. Before performing this procedure, make sure that the boot entries in NVRAM are in the following order:

    • EFI

    • OEM (optional)

    • MSR

    • Unknown OEM (platform flag is not set)

  4. Open Command Prompt (click Start, click Run, and then type cmd).

  5. Type:

    diskpart

  6. At the DISKPART prompt, type:

    list disk

    Make note of the disk numbers for the dynamic disks that will make up the mirrored volume.

  7. At the DISKPART prompt, type:

    select disk 1

    Disk 1 is an empty disk that you will mirror to the boot disk.

  8. At the DISKPART prompt, type:

    clean

  9. At the DISKPART prompt, type:

    convert gpt

  10. Delete the Microsoft Reserved (MSR) partition. At the DISKPART prompt, type:

    select partition 1

  11. At the DISKPART prompt, type:

    delete partition override

  12. Determine the size of the Extensible Firmware Interface (EFI) partition and the MSR partition on the boot disk. At the DISKPART prompt, type:

    select disk 0

  13. List the partitions on disk 0. At the DISKPART prompt, type:

    list partition

  14. Switch to disk 1. At the DISKPART prompt, type:

    select disk 1

  15. Create an EFI partition of the same size as that on disk 0. At the DISKPART prompt, type:

    create partition efi size=

  16. Create an MSR partition of the same size as that on disk 0. At the DISKPART prompt, type:

    create partition msr size=

  17. Mount the EFI partition on disk 0. At the DISKPART prompt, type:

    select disk 0

  18. At the DISKPART prompt, type:

    select partition 1

  19. At the DISKPART prompt, type:

    assign letter=m

  20. Mount the EFI partition on disk 1. At the DISKPART prompt, type:

    select disk 1

  21. At the DISKPART prompt, type:

    select partition 1

  22. At the DISKPART prompt, type:

    assign letter=n

  23. At the DISKPART prompt, type:

    exit

  24. Format the EFI on disk 1. At the command prompt, type:

    format n:/fs:FAT /q /y

  25. Copy all contents from the EFI on disk 0 to the EFI on disk 1. Use the /h option to copy the hidden files. At the command prompt, type:

    xcopym:\*.* n:\ /s /h

  26. Convert disk 0 and disk 1 to dynamic disks. At the command prompt, type:

    diskpart

  27. At the DISKPART prompt, type:

    select disk=1

  28. At the DISKPART prompt, type:

    convert dynamic

  29. At the DISKPART prompt, type:

    select disk=0

  30. At the DISKPART prompt, type:

    convert dynamic

    DiskPart displays the following message:

    You must reboot your computer to complete this operation.

  31. At the DISKPART prompt, type:

    exit

  32. Restart the computer. Wait for Windows to load and to prompt you to restart the computer a second time to complete the conversion of the boot disk to dynamic.

  33. Add a mirror to the boot volume. At the command prompt, type:

    diskpart

  34. At the DISKPART prompt, type:

    select volume=c

    Drive letter C is the boot volume, which is mirrored to disk 1 in the next step.

  35. At the DISKPART prompt, type:

    add disk=1

    Wait for the volume to synchronize.

  36. At the DISKPART prompt, type:

    exit

  37. Verify that there are 2 boot entries. At the command prompt, type:

    bootcfg

    The first entry is to boot to the first disk with the original EFI on disk 0. The second entry is to boot to the second disk with the original EFI on disk 0.

  38. Clone the EFI partition. At the command prompt, type:

    bootcfg /list

    Write down the first EFI partition’s globally unique identifier (GUID). You will need this in step 40.

  39. Clone the EFI partition. At the command prompt, type:

    bootcfg /list 1

    Write down the second EFI partition’s GUID. You will need this in step 40.

  40. At the command prompt, type:

    bootcfg /clone /sg GUID 1**/tg** GUID 2**/d+ clone_entry**

    Use double quotes if the description (/d argument) has spaces.

  41. Verify that the bootcfg /clone command created two entries in NVRAM. At the command prompt, type:

    bootcfg

    There should be 2 new entries, 4 total: two entries that use the EFI on disk 0, and two entries that use the EFI on disk 1.

Important

  • Consider creating an Automated System Recovery (ASR) set that you can use to restore the computer in case both halves of the mirrored system or boot volume become damaged. For more information about how to create an Automated System Recovery set, see Related Topics.

Notes

  • To perform this procedure on a local computer, you must be a member of the Backup Operators group, Administrators group, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as.

  • To open Computer Management, click Start, click Control Panel, double-click Administrative Tools, and then double-click Computer Management.

  • For additional information about converting basic disks to dynamic disks, see Related Topics.

  • After you convert a basic disk to a dynamic disk, you cannot change the dynamic volumes back to partitions. Instead, you must delete all dynamic volumes on the disk and then use the Convert To Basic Disk command. If you want to keep your data, you must first back it up or move it to another volume. For more information about the Convert To Basic Disk command, see Related Topics.

  • Before you convert disks, close any programs that are running on those disks.

  • Once converted, a dynamic disk will not contain basic volumes (primary partitions or logical drives), nor can it be accessed by MS-DOS, Windows 95, Windows 98, Windows Millennium Edition, Windows NT, or Windows XP Home Edition operating systems. You can access dynamic disks only with computers running Windows 2000, Windows XP Professional, or Windows Server 2003 operating systems.

  • When you convert a basic disk to a dynamic disk, any existing partitions or logical drives on the basic disk become simple volumes on the dynamic disk.

  • Do not convert basic disks to dynamic disks if they contain multiple operating systems (for example, if the disk is set up to dual boot with another operating system). After the disk is converted to dynamic, you will be able to start the operating system that you used to convert the disk, but you will not be able to start the other operating system(s) on the disk.

  • For the conversion to succeed, any master boot record (MBR) disks to be converted must contain at least 1 MB of free space at the end of the disk for the dynamic disk database. Windows 2000, Windows XP Professional, and Windows Server 2003 operating systems automatically reserve this space when creating partitions or volumes on a disk, but disks with partitions or volumes created by other operating systems might not have this space available. (This space might exist even if it is not visible in Disk Management.)

  • If there are any known original equipment manufacturer (OEM) partitions on the disk, they remain as basic partitions when you convert the disk to dynamic.

  • You can create mirrored volumes only on computers running Windows 2000 Server, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, or Windows Server 2003 operating systems.

  • You need two dynamic disks to create a mirrored volume.

  • Mirrored volumes are fault tolerant and use RAID-1, which provides redundancy by creating two identical copies of a volume.

  • Mirrored volumes cannot be extended.

  • Both copies (mirrors) of the mirrored volume share the same drive letter and mount points.

  • You can mirror the system and boot volumes to a different disk on the same controller or to a different disk on a different controller. Using one controller per disk is referred to as duplexing.

  • Before you mirror the system or boot volume in an x86-based computer, you must note the following guidelines:

    • Using Advanced Technology Attachment (ATA) disks for a mirrored system volume is supported, but the recovery procedure is more complicated when the master disk on the primary integrated device electronics (IDE) channel fails. In this case, you must move the disk with the remaining mirror to the primary IDE channel and set its jumper to master position.

    • Do not mirror the system volume by using an ATA disk with a SCSI disk because startup problems can occur if one of the disks fails.

    • If you use duplexed SCSI controllers, use identical controllers from the same manufacturer.

    • To ensure that the computer can start from the remaining mirror, you must test the mirrored system volume before a failure.

To break a mirrored boot volume

When you no longer require a mirrored boot volume or when a disk failure occurs, you can use this procedure to break the mirrored boot volume.

  1. Remove the disk that is no longer on the system. At the command prompt, type:

    diskpart

  2. At the DISKPART prompt, type:

    list disk

    Note the disk number of the disk that is missing. You will need this disk number in step 4.

  3. At the DISKPART prompt, type:

    select volume=c

  4. At the DISKPART prompt, type:

    **break disk=**disk number nokeep

  5. At the DISKPART prompt, type:

    list volume

  6. Verify that disk 0 is removed from the mirror and the existing disk is now a simple volume.

  7. At the DISKPART prompt, type:

    exit

  8. Clean up the boot configuration entries from the deleted disk. At the command prompt, type:

    bootcfg

    Note the entries in the boot list that are no longer valid (for example, ID 1) These are the entries that boot from the original EFI partition, not the new EFI partition.

See Also

Concepts

Converting a basic disk to dynamic
Partition styles
Dynamic disks and volumes
Using mirrored volumes
Format a dynamic volume
Assign, change, or remove a drive letter
Delete a dynamic volume
DiskPart
Checklists for Backing Up and Restoring Data
Automated System Recovery (ASR) overview
Create an Automated System Recovery set using Backup