Distributed File System

1
Chapter 5

• Distributed File System

2
Introduction to Dfs
3
Why DFS?

• Single
• Logical
• Hierarchical
• Gives end users a single point of reference for
  all network resources
• Regardless of location
• Ie. No \\instructor\xxxx
• Or Browsing the network to find resources
• Users do not need to know where resources are
  located

4
Advantages

• Simplifies network administration
• Use of a single namespace to access resources
  DFS root
• No additional memory requirements
• Integrated with the redirector
• Must install DFS client on WIN 9x
• File servers can be moved simply by updating
  the path in DFS

5
Advantages

• Load Balancing
• Extensible Namespace can easily be extended to
  include new disks, or other resources
• Client caching
• IIS integration

6
DFS Tree Structure

• Presents resources to the user in the familiar
• My Computer or
• Windows Explorer type format

7
Limits of Dfs

• 260 characters per file path
• 32 alternatives per volume
• 1 Dfs root per server
• Unlimited Dfs roots per domain
• Volumes limited by system resources

8
Overview of Dfs Roots

• The Dfs Service is auto-installed with the
  installation of Microsoft Windows 2000 Server.
• Two types of Dfs roots can be configured on
  Windows 2000 Server computers stand-alone and
  domain.

9
Stand-Alone Dfs Roots

• Stand-alone Dfs information is stored in the
  local registry.
• A stand-alone Dfs root permits a single level of
  Dfs links.
• When the Distributed File System snap-in is used
  to connect to existing stand-alone Dfs roots, all
  servers known to the browse list are retrieved
  because there is no unique NetBIOS name
  registered by Dfs-enabled servers.
• Stand-alone Dfs roots can be located on all
  supported file systems, although locating
  resources on NTFS-formatted partitions is
  recommended.
• Stand-alone Dfs roots offer no replication or
  backup the Dfs root represents a single point of
  failure.

10
Domain Dfs Roots

• Multiple servers hand out referrals for the Dfs
  namespace.
• A fault-tolerant Dfs root is stored in Active
  Directory services and is replicated to every
  participating Dfs root server. Changes to a Dfs
  tree are automatically synchronized with Active
  Directory services.
• Fault-tolerant roots must be located on NTFS
  version 5.0formatted partitions.
• The list of domains and servers is populated by
  querying the global catalog for all
  fault-tolerant Dfs roots.
• Dfs replication topology uses the existing Active
  Directory replication topology.

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Configuring a Stand-Alone Dfs Root

• Stand-alone Dfs stores the Dfs topology on a
  single computer and does not provide fault
  tolerance.
• A stand-alone Dfs root is physically located on
  the server that users initially connect to.
• To create a stand-alone Dfs root, use the
  Distributed File System snap-in to start the New
  Dfs Root wizard.

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Creating a Stand-Alone Dfs Root
13
Configuring a Domain Dfs Root

• Domain Dfs writes the Dfs topology to the Active
  Directory store, which allows links to point to
  multiple identical shared folders for fault
  tolerance.
• Domain Dfs supports DNS, multiple levels of child
  volumes, and file replication.
• To create a domain Dfs root, use the Distributed
  File System snap-in to start the New Dfs Root
  wizard.

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Configuring New Dfs Links

• Users can browse folders under a Dfs root without
  knowing where the referenced resources are
  physically located.
• After you create the Dfs root, you can create Dfs
  links.
• To create a Dfs link, use the Distributed File
  System snap-in to open the Create A New Dfs Link
  dialog box.

15
Creating a Dfs Link
16
Dfs Links
17
FRS Replication

• FRS is installed automatically on all Windows
  2000 Server computers.
• FRS is configured to start automatically on all
  domain controllers and manually on all
  stand-alone and member servers.
• The Active Directory store uses FRS to
  synchronize the directory among all the domain
  controllers.
• Active Directory services automatically generates
  a ring topology for replication among domain
  controllers in the same domain.
• The ring structure ensures that there are at
  least two replication paths from one domain
  controller to another.

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FRS Replication

• Replicating SYSVOL
• Replicating DFS roots
• Inter-site replication

19
Replication

• Additional sites built their own replication
  topologies
• Site links need to be created manually
  (transports)
• Inter-site connection objects created
  automatically

Microsoft
Sales
MS3
MS1
MS4
MS2
Sales1
Sales3
Sales2
Site Redmond
Site Paris
20
What Is a Site?

• Collection of one or more subnets, defined by the
  administrator. It is assumed that they are
  well-connected high-bandwidth local area
  network (LAN) connections.
• Sites may contain multiple domains
• Domain may span more than one site.
• Sites are limited to a single forest.
• First domain controller in a forest, new site is
  created by default (Default-First-Site-Name). An
  administrator can create other sites.

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Sites
22
Intra-Site Replication

• Intra-site replication occurs between domain
  controllers within a site.
• Replicated data is not compressed.
• The default replication interval is five minutes.
• Replication is trigger-based (notification and
  pull).

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Inter-Site Replication

• Inter-site replication occurs between domain
  controllers in different sites.
• You can specify the time when inter-site
  replication should occur. The default replication
  interval is three hours.
• You can specify the network transport for use in
  inter-site replication.
• Inter-site replication is compressed, regardless
  of the transport used.
• Inter-site replication compression reduces the
  data on the network by 88 to 90 percent.
• Inter-site replication is not configured
  automatically it must be configured by an
  administrator.

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Knowledge Consistency Checker (KCC)

• The KCC generates a ring topology for replication
  among domain controllers in the same domain.
• The ring structure guarantees that there are at
  least two replication paths from one domain
  controller to another.
• The KCC analyzes the replication topology within
  a site to ensure that the replication topology is
  efficient.

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Unique Sequence Numbers (USNs)

• When a directory object is updated at a domain
  controller, a USN is assigned.
• When the domain controller writes the change into
  the directory, it also writes the USN.
• Each domain controller maintains a table of the
  USNs that it receives from every other domain
  controller in the domain.
• USNs eliminate the need for precise time stamps
  for changes.
• USNs simplify recovery after a failure.

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Replicating SYSVOL

• Changes to the systemroot\SYSVOL folder on any
  domain controller are automatically replicated to
  other domain controllers within the site.
• The replication topology and process are separate
  but identical to Active Directory replication.
• Windows 2000 Server sets up a default folder
  structure for SYSVOL.

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Replicating Dfs Fault-Tolerant Roots

• Dfs and file replication support a number of
  features.
• Each Dfs root or link can reference a replicated
  set of shared resources.
• Dfs replication is disabled by default use the
  Distributed File System snap-in to enable
  replication.
• Multimaster replication can be modified by any
  replica
• NTFS shares can be replicated
• Others must publish alternates no replication

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Configuring FRS for Inter-Site Replication

• Use the Active Directory Sites And Services
  snap-in to configure inter-site replication.
• To configure the FRS settings, you must create a
  new site link for the inter-site transport
  protocol listed in the console tree.