Examining Windows Server 2003 File System Services

There are many ways to create fault tolerance for a file system using services and file system features included in the Windows Server 2003 family of operating systems. Depending on whether security, automated data archival, simplified file server namespaces, data replication, or faster data recovery is the goal, Windows Server 2003 provides file system features and services that can enhance any computing environment.

Distributed File System

In an effort to create highly available file services that reduce user configuration changes and file system downtime, Windows Server 2003 includes the Distributed File System (DFS) service. DFS provides access to file data from a unified namespace that redirects users from a single network name to shared data hosted across various servers. For example, \\companyabc.com\home could redirect users to \\server3\home$ and \\server2\users. Users benefit from DFS because they need to remember only a single server or domain name to locate all the necessary file shares. When deployed in a domain configuration, DFS can be configured to replicate data between servers using the File Replication Service.

Distributed File System Replication

With the release of Windows 2003 R2, Microsoft updated DFS to a new revision called Distributed File System Replication, or DFSR. DFSR uses the core technology from which DFS was built, and adds more functionality for better replication processes, algorithms, and capabilities. DFSR commonly is simply called DFS because most organizations that have been using DFS since Windows 2000 and the original release of Windows 2003 have been calling the service DFS. In terms of this book, the reference to DFS and DFSR is interchangeable, with updated references to DFSR being noted throughout this chapter.

File Replication Service

The File Replication Service (FRS) is automatically enabled on all Windows 2000 and Windows Server 2003 systems but is configured to automatically start only on domain controllers. On Windows 2000 and Windows Server 2003 domain controllers, FRS is used to automatically replicate the data contained in the SYSVOL file share, including system policies, Group Policies, login scripts, login applications, and other files that administrators place in the SYSVOL or the Netlogon shares. When a domain controller is added to a domain, FRS creates a connection or multiple connections between this server and other domain controllers. This connection manages replication using a defined schedule. The default schedule for domain controller SYSVOL replication is always on. In other words, when a file is added to a SYSVOL share on a single domain controller, replication is triggered immediately with the other domain controllers it has a connection with. When domain controllers are in separate Active Directory sites, the FRS connection for the SYSVOL share follows the same schedule as Active Directory. The SYSVOL FRS connection schedule is the same as the site link. Domain-based DFS hierarchies can also use FRS connections to replicate file share data for user-defined shares.

Although FRS and domain DFS provide multi-master automated data replication, the Volume Shadow Copy service can be used to manage the actual content or data contained within the shares.

Volume Shadow Copy Service

The Volume Shadow Copy service (VSS) is new to Windows Server 2003 and provides file recoverability and data fault tolerance never previously included with Windows. VSS can enable administrators and end users alike to recover data deleted from a network share without having to restore from backup. In previous versions of Windows, if a user mistakenly deleted data in a network shared folder, it was immediately deleted from the server and the data had to be restored from backup. A Windows Server 2003 volume that has VSS enabled allows a user with the correct permissions to restore that data from a previously stored VSS backup. Using VSS on a volume containing a shared folder, the administrator can simply restore an entire volume or share to a previous state, or just restore a single file.

Remote Storage

To provide hierarchical storage management services, including automated data archiving, Windows Server 2003 includes the Remote Storage service first introduced in Windows 2000 Server. This service can be configured to migrate data from a disk volume to remote storage media based on last file access date, or when a managed disk reaches a predetermined free disk space threshold, data can be migrated to remote media automatically. Although this service does not provide file system fault tolerance, using Remote Storage to manage a volume can improve reliability and recoverability by keeping disk space available and by reducing the amount of data that needs to be backed up or restored when a disk failure occurs.

Note

Do not configure Remote Storage to manage volumes that contain FRS replicas because doing so can cause unnecessary data migration. Periodically, FRS may need to access an entire volume to send a complete volume copy to a new server replica, and this can create several requests to migrate data back to a disk from remote storage media. This process can be lengthy because all the managed volumes' migrated data may need to be restored to the server's physical disk.