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Create and test a mirrored system or boot volume

Updated: January 21, 2005

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

To create and test a mirrored system or boot volume (32-bit only)

To ensure that your x86-based computer can load Windows if one of the disks or controllers fails, you can mirror the system volume. This makes an exact copy of the volume that contains the hardware-specific files needed to load Windows. You can also mirror the boot volume. This makes an exact copy of the volume that contains the Windows operating system.

To create a mirrored system or 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.

  3. Open Computer Management (Local).

  4. In the console tree, click Computer Management (Local), click Storage, and then click Disk Management.

  5. If the system or boot volume already resides on a dynamic disk, skip to step 6. Otherwise, you must convert the disk to a dynamic disk before you can mirror it.

    How?

    1. Right-click the disk that contains the system or boot volume and click Convert to Dynamic Disk.

      Caution

      Do not convert basic disks to dynamic disks if they contain multiple operating systems (for example, the disk is set up to dual boot with another operating system). After the disk is converted to dynamic you can 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.

    2. In the Convert to Dynamic Disk dialog box, select the basic disk you want to convert to dynamic and then click OK.

    3. In the Disks to Convert dialog box, click Convert.

    4. In the Disk Management dialog, click Yes.

    5. In the Convert Disk to Dynamic dialog box, click Yes.

    6. In the Confirm dialog box, click OK to restart your computer.

    7. After your computer restarts, log on. On the System Settings Change dialog box, click Yes to restart your computer again.

    8. After your computer restarts, log on.

    9. Open Computer Management (Local).

    10. In the console tree, click Computer Management (Local), click Storage, and then click Disk Management.

      Continue to step 6.

  6. Right-click the system or boot volume and click Add Mirror.

  7. In the Add Mirror dialog box, select an unallocated dynamic disk with enough free space to mirror the system or boot volume and click Add Mirror.

    Disk Management resynchronizes both disks. When resynchronization is complete, the system or boot volume is a fault-tolerant mirrored volume.

Important

  • Because a problem might go undetected until you try to restart the computer from the second disk, you must create a Windows startup floppy disk that you can use to start Windows on the remaining mirror. In addition, you should recreate your startup floppy disk after you add or remove volumes on the disk that contains the boot volume, after you convert the disk to dynamic, or after you install a Windows service pack.

  • 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, 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.)

  • 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.

  • For more information about how to mirror the system or boot volume, see "Disk Management" at the Microsoft Resource Kits Web site.

To test a mirrored system or boot volume

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

  2. Read and understand all of the information in the Notes section.

  3. Shut down the computer, and then disconnect or turn off one of the disks to simulate the failure of a disk.

  4. Restart the computer by using the remaining mirror.

  5. After you verify that Windows starts correctly, shut down the computer and reconnect the disk.

  6. Restart the computer. When the boot menu appears, select the mirror on the disk that remained connected.

  7. Open Computer Management (Local).

  8. In the console tree, click Computer Management (Local), click Storage, and then click Disk Management.

  9. Right-click the disk that has any of the volumes marked Failed Redundancy, and then click Reactivate Disk.

  10. After the mirrors are resynchronized, shut down the computer and repeat steps 1 through 9 using the other disk.

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.

  • In Steps 4 and 6, the Windows can start from the remaining mirror if all of the following conditions are met:

    • In SCSI systems, the remaining disk must be the first disk specified by the SCSI controller. If other disks are present and the remaining mirror is on the same SCSI controller as the failed disk, the BIOS for that controller must support specifying the boot device from any disk on the controller. If other disks are present and the remaining mirror is on a different controller, the original controller must support turning off the BIOS, and the mirror’s controller must support specifying the boot device from any disk on the controller.

    • In SCSI systems, both SCSI controllers must have translation options set identically, either both enabled or both disabled.

    • In IDE systems, the disk that contains the remaining mirror must be the master disk on the primary IDE controller. You can move the remaining disk to this position if the master disk on the primary controller fails. Set the jumper to the master position, if necessary.

    • The disk remaining after a failure must contain a valid system volume that is marked active and must contain a valid Boot.ini file along with Ntldr and Ntdetect.com.

  • When you mirror the boot volume, operating systems in the Windows Server 2003 family usually automatically update Boot.ini. If Windows cannot update Boot.ini, as when the BIOS for the second SCSI controller is disabled, you see a message instructing you to update Boot.ini manually. Therefore, to ensure that the computer can start from the remaining mirror, you need to verify that the information in Boot.ini is correct before a failure occurs, especially if you manually make changes to Boot.ini.

    For example, if you use the Signature syntax to specify the disk that contains the boot volume and that disk fails, the computer does not start because the system is looking for the disk with this particular signature. For this reason, you need to use Multi syntax to specify the disk that contains the boot volume. For more information about Boot.ini, Signature syntax, and Multi syntax, see "Troubleshooting Startup" at the Microsoft Resource Kits Web site.

  • When you break a mirrored system or boot volume using the Disk Management snap-in, you must select the disk in the mirrored volume that was used to start the computer. Disk Management retains the volume on the selected disk, which keeps its drive letter and becomes a simple volume. The other disk in the mirrored system or boot volume receives the next available drive letter and becomes a new simple volume.

    When breaking a mirrored system or boot volume using the DiskPart command, however, you must specify the disk in the mirrored system or boot volume that was not used to start the computer. The disk used to start the computer keeps the mirrored volume’s drive letter and becomes a simple volume, while the specified disk receives the next available drive letter and becomes a simple volume.

  • For more information about how to test a mirrored the system or boot volume, see "Disk Management" at the Microsoft Resource Kits Web site.

Information about functional differences

  • Your server might function differently based on the version and edition of the operating system that is installed, your account permissions, and your menu settings. For more information, see Viewing Help on the Web.

See Also

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