• Illustration: Data Protection Manager System Architecture

Data Protection Manager (DPM, formerly called Data Protection Server) 2006—a new server product that provides Windows file servers with an intermediate hard-disk-based backup and restore facility—is now shipping. DPM reduces exposure to lost data by taking backups many times per day, dramatically reduces file restore times, and lets users restore files without IT assistance. However, the first release does not provide long-term archival or disaster recovery and protects ordinary files only—it cannot back up specialized data stores, such as the Windows Registry, Exchange, and SQL Server. It also will not run natively on 64-bit versions of Windows.

Overcoming Limitations of Traditional Tape Backup

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

Difficulty backing up servers in branch offices. Backing up data stored on branch office servers poses a dilemma. These offices generally do not have anyone with IT skills to manage sets of backup tapes, yet the bandwidth of their WAN connections is insufficient to copy huge volumes of data for backup to tape in a central data center.

Loss of recent data. Tape-based backups are rarely performed more frequently than once a day, meaning that any data changed since the backup will be lost in the event that the server must be restored from tape. In addition to the loss of productivity, such data losses can have other serious business ramifications.

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 time is unproductive for the user, help desk, and data-center personnel.

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

The new Volume Shadow Copy Service (VSS) that comes on Windows Server 2003 helps solve the problem of the loss of recent data by taking "snapshots" of data at more frequent intervals. The problem of long restore times is solved by allowing authorized users to restore earlier versions of files without requiring an administrator to load tapes. However, VSS cannot be retrofitted to Windows 2000 Server systems. Since it may take several years before the bulk of Microsoft customers have migrated their servers to Windows Server 2003, DPM can back up files on Windows 2000 servers and provide those customers with some of the benefits of VSS.

Although VSS coupled with a VSS-enabled tape backup agent generally eliminates many backup issues related to backing up live application databases and getting consistent system state information, VSS does not solve the problem of high loads on servers and networks. In the case of a heavily used server containing large amounts of data, the tape backup agent can noticeably impact the performance of the server, yet also take so long to move its data to the tape server that the daily backup cycle cannot complete before the next day's backup is scheduled to commence.

DPM Technology

The DPM system consists of a Windows Server 2003 computer, or a Network Attached Storage (NAS) device running the Windows Storage Server 2003 OS, equipped with a large amount of disk storage and running the DPM software, plus a DPM agent running on each server it protects.

Each agent monitors and accumulates byte-level changes to the server's files over a one-hour period, then transfers those changes as a batch to the DPM server, where DPM merges the accumulated changes into the corresponding replicas stored in a large disk-based repository. Because the amount of data in each batch is relatively low and replication has until the next transfer period to complete, this replication works fine over lower-bandwidth WAN connections. This makes it possible to use DPM to protect data on branch office servers.

The VSS system on the DPM computer also takes periodic (e.g., hourly) snapshots of the replicas. Because VSS storage only grows by the amount of data that has changed, Microsoft claims that 90 days of data stored on a DPM computer requires only two to three times more disk storage (on average) than the sum of the data of all the servers it protects.

Since the data on DPM consists of replicas, organizations can make tape backups of the DPM server data at any time without affecting the performance of the production servers. Special DPM-aware tape backup products are available from vendors such as Computer Associates and CommVault, but any VSS-aware tape backup program can be made to work. The DPM server can also host the tape backup server and tape media, or it can run a remote backup agent that copies the snapshots to a separate backup server (typically over a dedicated backup network to avoid slowing down the production network.)

DPM provides an administrative interface to configure policy options, schedules, replication settings, and other choices. One attractive option: end users can use Windows Explorer extensions for Windows XP and Windows 2000 Workstation, or "File Open" dialog boxes in Office 2003, to connect to a DPM 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 Manager System Architecture".)

Packaging, Pricing, and Licensing

Introduced under Microsoft's "Systems Center" management product brand, DPM uses a licensing model similar to that of Microsoft Operations Manager (MOM) 2005, which requires a Base License for the server running MOM and an Operations Management License (OML) for each managed server. DPM's estimated retail price is US$950, which includes one server Base License and Data Protection Management Licenses (DPMLs) to protect three file servers. Additional DPMLs have an estimated retail price of US$189, although volume licensing can drop this below US$150.

DPM is available in Chinese (Traditional and Simplified), English, French, German, Italian, Japanese, Korean, and Spanish versions.

Although DPM is a software-only product, numerous Microsoft storage and backup partners are shipping, or have announced, hardware appliances built on DPM or tape backup and archival applications integrated with DPM. These partners include Advanced Micro Devices, CommVault, Computer Associates, Dell, EqualLogic, Fujitsu Siemens, Hewlett-Packard, Intel, Quantum, and Yosemite.

Serious Limitations in First Release

DPM 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.

In fact, in most cases tape will also be required to compensate for limitations in the first edition of DPM. DPM can replicate normal files only, which excludes live databases such as Exchange, SQL Server, and the Windows Registry. Because it cannot back up the system state contained in the Registry and several other OS files, DPM cannot be the sole means of backing up a server if the organization wants the ability to restore a server to its last good state; the servers must still run traditional tape backup agents to capture this information and send it to a tape backup server. (Organizations could adopt a split backup strategy of using a backup agent to capture only the system state, OS files, and other database data directly to tape, while using DPM to back up application and data files to disk. Although this approach would yield some of the benefits of DPM, it would add complexity if a full server restore should be required.)

This release of DPM imposes another restriction on organizations that want to use DPM to back up servers in remote locations via their WAN: the servers being backed up and the DPM server must reside in the same Active Directory (AD) domain. Organizations that built forest-level AD structures with separate domains for the servers in remote locations cannot consolidate backup of those servers using a central DPM computer.

Microsoft says that DPM complies with the company's Common Engineering Criteria (CEC) specification, a set of internal engineering requirements designed to ensure better levels of integration and operational consistency across Windows Server System products. Although the DPM product group has issued a MOM Management Pack for monitoring DPM systems (a key provision of the CEC), the CEC's 64-bit support provision is met only in that the DPM server and the DPM agents that run on each protected server will run using the Windows 32 on Windows 64 (WOW 64) 32-bit emulation mode of x64 and IA-64 versions of the Windows Server 2003 OS. Neither can run as a native 64-bit application. Although this limitation may not have a significant impact on the servers running the DPM agents, it does mean that the DPM server itself cannot fully exploit the increased power of 64-bit systems.

Microsoft intends to rectify these limitations in future editions.

Resources

The DPM home page, with a link to a trial version, is www.microsoft.com/dpm.

The VSS feature of Windows Server 2003 is described in "Windows .NET Server Supports Enterprise Storage" on page 3 of the Dec. 2002 Update.

The goal and specific details of Microsoft's Common Engineering Criteria are described in "Common Criteria Promote Consistency" on page 7 of the Aug. 2004 Update.