Using the Distributed File System Replication


To improve the reliability and availability of file shares in an enterprise network, Microsoft has developed the Distributed File System. DFS improves file share availability by providing a single, unified namespace to access shared folders hosted across different servers. A user needs to remember only a single server or domain name and share name to connect to a DFS shared folder.

Note

As noted earlier in this chapter, with the release of Windows 2003 R2, Distributed File System is now called Distributed File System Replication, or DFSR. Because DFS and DFSR are commonly referenced interchangeably, this section of the chapter will also use the references DFS and DFSR interchangeably.


Benefits of DFSR

DFSR has many benefits and features that can simplify data access and management from both the administrator and user perspective. DFS inherently creates a unified namespace that connects file shares on different servers to a single server or domain name and DFS link name, as shown in Figure 30.12. Using Figure 30.12 as an example, when a user connects to \\SERVER2\UserData, he will see the software folder contained within. Upon opening this folder, the user's DFS client will redirect the network connection to \\Server99\downloads, and the user will remain unaware of this redirection.

Figure 30.12. A standalone DFS root with a link targeting a different server.


Because end users never connect to the actual server name, administrators can move shared folders to new servers, and user logon scripts and mapped drive designations that point to the DFS root or link do not need to be changed. In fact, a single DFS link can target multiple servers' file shares to provide redundancy for a file share. This provides file share fault tolerance; because clients will be redirected to another server, the current server becomes unavailable. The DFS client will frequently poll the connected server and can redirect the user connection if the current server becomes unavailable.

When a domain-based DFS root is created, the file shares associated with a link can be automatically replicated with each other. When users attempt to access a replicated DFS share, they will usually be connected to a server in the local Active Directory site but can connect to remote sites as needed. Before we discuss DFS any further, we should define some key terms used by the Distributed File System and the File Replication Service.

DFS Terminology

To properly understand DFS, you must understand certain terms that are commonly used in referencing DFS configurations. These terms, described next, are frequently used to refer to the structure of a DFS configuration, and at times, the terms are actually part of the DFS configuration.

  • DFS root The top level of the DFS tree that defines the namespace for DFS and the functionality available. DFS roots come in two flavors: standalone root and domain root. A standalone root can be accessed by the server name on which the root was created. The domain root can be accessed by the domain name that was specified when the root was created. A domain-based root adds fault-tolerant capabilities to DFS by allowing several servers to host a replica of a DFS link. See more detailed explanations later in this chapter.

  • DFS link The name by which a user connects to a share. You can think of a link as the DFS share name because this is the name users will connect to. DFS links redirect users to targets.

  • Target The actual file share that is hosted on a server. Multiple targets can be assigned to a single DFS link to provide fault tolerance. If a single target is unavailable, users will be connected to another available target. When domain-based DFS links are created with multiple targets, replication can be configured using the File Replication Service to keep the data across the targets in sync.

  • DFS tree The hierarchy of the namespace. For example, the DFS tree begins with the DFS root name and contains all the defined links below the root.

  • Referral A redirection that allows a DFS client to connect to a specified target. Disabling a target's referral keeps it from being used by clients. Target referral can be disabled when maintenance will be performed on a server.

FRS Terminology

DFS uses the File Replication Service to automatically replicate data contained in DFS targets associated with a single root or link on which replication has been configured. To understand the replication concepts, you must understand some key FRS terminology. Here are some important terms:

  • Replication The process of copying data from a source server file share to a destination server file share. The file shares are replicated through replication connections.

  • Replication connection The object that manages the replication between a source and destination server. The replication connection defines the replication schedule and the source and destination replication partners, for example. Each replication connection has only a single source and destination replication partner.

  • Replication partner A server that shares a common replication connection. The inbound replication partner receives data from a server specified in the replication connection. The outbound replication partner sends data to the replication partner specified in the replication connections.

  • Replica A server that hosts a file share in which FRS replication is configured.

  • Replica set All the servers that replicate a given file share or folder with one another.

  • Multimaster replication The process that occurs when any replica in a replica set updates the contents of a replicated shared folder. Every replica can be the master, and every replica can be a slave. FRS replication defaults to multimaster, but replication connections can be configured to provide master-slave replication.




Microsoft Windows Server 2003 Unleashed(c) R2 Edition
Microsoft Windows Server 2003 Unleashed (R2 Edition)
ISBN: 0672328984
EAN: 2147483647
Year: 2006
Pages: 499

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