Setup Disk Mirroring on Windows 2000 Dynamic Disks

This article explains how Microsoft Windows 2000 manages software-based RAID-1 disk mirroring using dynamic storage architecture. It covers the core requirements of the Logical Disk Manager, the step-by-step procedure for creating a mirrored volume in Disk Management, the configuration needed to make system and boot mirrors bootable, and how the operating system handles drive failures and mirror maintenance.

Overview of Dynamic Storage in Windows 2000

Windows 2000 introduced dynamic disks, managed by the Logical Disk Manager (LDM), to replace traditional basic disks for software-based fault tolerance. In Windows 2000, software RAID-1 (mirroring) cannot be created on basic disks; both the source and target storage devices must be configured as dynamic disks.

Dynamic disks use a hidden 1 MB database located at the end of the physical drive to store volume layout information. When drives are grouped together, this database replicates across all dynamic disks on the system, allowing the OS to track volume status automatically.

Prerequisites for Disk Mirroring

Before configuring a mirrored volume, the system must meet the following criteria:

  • At least two physical hard drives must be installed.
  • Both disks must be converted to dynamic disks.
  • The secondary disk must contain unallocated space equal to or larger than the volume you intend to mirror.
  • The secondary disk must use an identical sector size to the primary disk.

To convert a basic disk to a dynamic disk:

  1. Open Computer Management and navigate to Disk Management.
  2. Right-click the target basic disk and select Upgrade to Dynamic Disk (or Convert to Dynamic Disk).
  3. Follow the prompt to complete the conversion without requiring a reboot (unless converting a system or boot disk).

Step-by-Step Mirror Setup

  1. Open Disk Management (diskmgmt.msc).
  2. Identify the existing dynamic volume you wish to protect with redundancy.
  3. Right-click the volume and select Add Mirror.
  4. In the dialog box, select the destination dynamic disk with sufficient unallocated space.
  5. Click Add Mirror.

Once initiated, Windows 2000 begins a background synchronization process known as "resilver." During this phase, the status displays as Regenerating. When data replication finishes, both disks display a status of Healthy, forming a single logical volume across two physical partitions.

Mirroring the System and Boot Volumes

Windows 2000 allows mirroring of the system volume (containing hardware-specific files like NTLDR and boot.ini) and the boot volume (containing the \WINNT directory). However, mirroring these volumes requires manual modification of the boot.ini file on the secondary drive to ensure the system can boot if the primary drive fails physically.

  1. Open boot.ini located at the root of the system drive.
  2. Duplicate the operating system line under the [operating systems] section.
  3. Modify the Advanced RISC Computing (ARC) path to point to the secondary disk’s controller, disk, and partition numbers: 
    multi(0)disk(0)rdisk(1)partition(1)\WINNT="Windows 2000 (Mirror Boot)"
  4. Copy the updated boot.ini, along with NTLDR and NTDETECT.COM, to the secondary disk's mirrored partition.

If the primary physical disk fails, the administrator can select the secondary boot option from the OS loader menu during system startup.

Managing and Recovering Mirrored Volumes

When a disk in a mirror set fails, Windows 2000 flags the affected volume as Failed Redundancy. The system continues operating using the single surviving drive. To restore redundancy:

  • Remove Mirror: If the primary or secondary disk has permanently failed, right-click the remaining healthy volume and choose Remove Mirror to isolate the functional volume as a simple volume.
  • Break Mirror: If you want to divide an intact mirror into two independent, identical volumes, choose Break Mirror. Both drives retain their data and become standalone simple volumes.
  • Replace and Re-mirror: After physically replacing a defective drive, convert the new replacement drive to a dynamic disk, right-click the existing functional volume, and select Add Mirror to rebuild fault tolerance.