• Illustration: Data Protection Server System Architecture

Data Protection Server (DPS), a new Microsoft server product planned for the second half of 2005, will provide Windows-based file servers with an intermediate hard disk–based backup-and-restore facility before data is backed up onto tape. DPS will allow backups to be taken many times per day, dramatically reduce file restore times, and let users restore files without IT assistance. However, the first release will protect ordinary files only; it will not back up all data on the server and will exclude data in databases such as the Windows Registry, Exchange, and SQL Server.

A public beta release of DPS is scheduled for the first quarter of 2005.

Overcoming Limitations of Traditional Tape Backup

DPS is designed to mitigate some traditional tape backup problems, including the following:

Long restore times and increased IT workload. When restoring data from tape, a data-center operator must locate and mount the correct tape, find the files or directories in question, and restore them to either the original location or an alternate location. This process results in lost productivity for the user, help desk, and data-center personnel.

Loss of recent data. Tape-based backups are rarely performed more frequently than once per day, meaning that any data changed since the backup will be lost during a restore from tape. This results in even more lost productivity and can have serious business ramifications.

High loads on servers and network during backup. When backing up to tape, the processor on the server being backed up is heavily loaded; this can affect users of that server when the backup occurs during work hours. Furthermore, the network between it and the backup server can also become so busy that users are impacted, especially when the traffic must cross a WAN link.

Although the new Volume Shadow Copy Service (VSS) that comes on Windows Server 2003 helps solve the first two problems, VSS cannot be retrofitted to Windows 2000 Server systems. Since it will be many years before the bulk of Microsoft customers have migrated their servers to Windows Server 2003, DPS can back up files on Windows 2000 servers and provide some of the benefits of VSS.

DPS Technology

The DPS system will consist of a Windows Server 2003 computer equipped with a large amount of disk storage and running the DPS software, plus DPS agents running on each server it protects.

The agents will monitor and copy byte-level changes to the files on the production servers, then periodically replicate only changed data to the DPS server, which will store it in a large disk-based repository. The VSS system on the DPS computer will take periodic (e.g., hourly) snapshots of its file system. Because VSS storage only grows by the amount of data that has changed, Microsoft claims that to keep 90 days of data on the DPS computer, it will require only two to three times more disk storage than the sum of the data of all the servers it protects.

Since the data on DPS will consist of replicas, organizations will be able to make tape backups of the DPS server data at any time without affecting production servers. DPS-enabled tape backup products will be available from vendors such as Computer Associates and CommVault. The DPS server will be able to perform as the tape backup server or run a remote backup agent that copies selected snapshots to a separate backup server over the network, which can also be separated from the production network.

DPS will provide an administrative interface to configure policy options, schedules, replication settings, and so on. One attractive option: end users will be able to use Windows Explorer extensions for Windows XP and Windows 2000 Workstation, or "File Open" dialog boxes in Office 2003, to connect to the DPS server, navigate to the replica of the server they need to restore data from, and copy or open snapshots of any files for which they have read permissions.

(For a graphical illustration of the way the system works, see "Data Protection Server System Architecture".)

Serious Limitations in First Release

DPS is not intended to replace tape backup. Tape is still needed for offsite data storage for disaster-recovery purposes and to meet requirements for long-term data retention and archival policies that conform to government regulations.

Although the need for tape is by design, the first edition of DPS has other limitations that will reduce its overall appeal for many customers. DPS can replicate normal files only, which excludes live databases such as Exchange, SQL Server, and the Windows Registry. Because it cannot store the system state contained in the Registry and several other OS files, DPS cannot be the sole means of backing up a server, so the servers still must run tape backup agents to capture this information and send it to a tape backup server.

While organizations might be tempted to use DPS to back up servers in remote locations via their WAN, DPS imposes another restriction: the server being backed up and the DPS server must reside in the same Active Directory domain. This means that organizations that built forest-level structures with separate domains for their remote locations cannot consolidate backup to a central DPS computer.

Microsoft intends to rectify these limitations in future editions.

Resources

Preliminary information on DPS can be found at www.microsoft.com/windowsserversystem/dps.

To learn more about VSS in Windows Server 2003, see "Windows .NET Server Supports Enterprise Storage" on page 3 of the Dec. 2002 Update.