Windows 2000 Striping with Parity on Dynamic Disks

Microsoft Windows 2000 manages disk striping with parity—commonly known as software RAID-5—through its Dynamic Disk architecture and the Logical Disk Manager (LDM). This article explains how Windows 2000 implements fault-tolerant striped volumes, detailing the underlying disk architecture, operating system requirements, parity calculation methods, and recovery procedures for failed drives.

Dynamic Disks and the Logical Disk Manager

Windows 2000 introduced Dynamic Disks to replace the traditional partition-table model used by Basic Disks. Dynamic Disks do not rely on the Master Boot Record (MBR) partition table to track individual volume boundaries. Instead, Windows 2000 places a 1 MB Logical Disk Manager (LDM) database at the very end of each dynamic physical disk.

The LDM database stores configuration metadata for all dynamic volumes on the computer. When changes occur—such as extending a volume or handling a drive offline—the LDM synchronizes this metadata across all connected dynamic disks. This architecture allows the operating system to assemble complex software RAID configurations, including striped sets with parity, without hardware RAID controllers.

Volume Configuration and System Requirements

Creating a striped volume with parity in Windows 2000 requires specific OS editions and hardware conditions:

  • Operating System Support: Only server editions—Windows 2000 Server, Advanced Server, and Datacenter Server—can create and manage RAID-5 volumes. Windows 2000 Professional cannot create striping with parity volumes.
  • Disk Count: A minimum of three dynamic disks is required, with a maximum limit of 32 disks per volume.
  • Storage Allocation: Each participating dynamic disk must supply an equal amount of unallocated dynamic space. The total usable storage capacity equals the size of one individual disk segment multiplied by the number of disks minus one ((n - 1) * size).

System and boot partitions cannot reside on a striped volume with parity in Windows 2000; the volume can only be used for data storage.

How Striping with Parity Functions

Windows 2000 handles striped volumes with parity by interleaving data in fixed stripes (typically 64 KB) across all participating dynamic disks.

  1. Parity Calculation: Parity is computed using a bitwise Exclusive OR (XOR) logic across the corresponding data blocks on the drives.
  2. Rotating Parity Blocks: Rather than dedicating a single physical disk to parity—which would create a write bottleneck—Windows 2000 distributes the parity blocks cyclically across all disks in the array.
  3. Write Operations: Every write to a parity stripe requires reading the old data and old parity, recalculating the new parity via XOR, and writing the new data and parity back to the disks.

Fault Tolerance and Volume Recovery

If a single physical drive in the dynamic array fails, the volume status changes to "Failed Redundancy" in the Disk Management console (diskmgmt.msc). The file system remains online and accessible to users:

  • Read Operations: Reads aimed at the missing disk are reconstructed dynamically in system memory by applying XOR math to the remaining functional data and parity blocks. This causes elevated CPU usage and slower I/O performance until the array is restored.
  • Repair Process: To restore redundancy, an administrator must install a replacement drive, convert it to a Dynamic Disk, open Disk Management, right-click the degraded volume, and select Repair Volume. The operating system then reads the surviving disks, calculates the missing data, and writes the reconstructed blocks onto the new dynamic disk.