What are the FSMO Roles ?

Flexible Single Master Operations (FSMO) has five roles

1. PDC emulator (one per domain)

2. Infrastructure master (one per domain)

3. Relative ID (RID) master (one per domain)

4. Schema master (one per forest)

5. Domain naming master (one per forest)

Schema Master

RID Master

Domain Naming Master

Infrastructure Master

PDC Emulator

FSMO RoleScopeFunction and availability requirementsSchema Master Enterprise

• Used to introduce manual and programmatic schema updates, and this includes those updates that are added by Windows ADPREP /FORESTPREP, by Microsoft Exchange, and by other applications that use Active Directory Domain Services (AD DS).
• Must be online when schema updates are performed.

Domain Naming Master Enterprise

• Used to add and to remove domains and application partitions to and from the forest.
• Must be online when domains and application partitions in a forest are added or removed.

Primary Domain Controller Domain

• Receives password updates when passwords are changed for the computer and for user accounts that are on replica domain controllers.
• Consulted by replica domain controllers that service authentication requests that have mismatched passwords.
• Default target domain controller for Group Policy updates.
• Target domain controller for legacy applications that perform writable operations and for some admin tools.

RID Domain

• Allocates active and standby RID pools to replica domain controllers in the same domain.
• Must be online for newly promoted domain controllers to obtain a local RID pool that is required to advertise or when existing domain controllers have to update their current or standby RID pool allocation.

Infrastructure Master DomainApplication partition

• Updates cross-domain references and phantoms from the global catalog. For more information, Phantoms, tombstones and the infrastructure master
• A separate infrastructure master is created for each application partition including the default forest-wide and domain-wide application partitions created by Windows Server2003 and later domain controllers. The Windows Server2008 R2 ADPREP /RODCPREP command targets the infrastructure master role for default DNS application in the forest root domain. The DN path for this role holder is CN=Infrastructure,DC=DomainDnsZones,DC=<forest root domain>,DC=<top level domain> and CN=Infrastructure,DC=ForestDnsZones,DC=<forest root domain>,DC=<top level domain>.

Flexable Single Master Operation Roles (FSMO) :

are five special roles which are vital for the smooth running of AD as a multimaster system.  These roles are installed automatically when AD service is installed.

The FSMO roles are as follows:

Schema Master:

The schema is shared between every Tree and Domain in a forest and must be consistent between all objects. The schema master controls all updates and modifications to the schema.

Domain Naming Master:

When a new Domain is added to a forest the name must be unique within the forest. The Domain naming master must be available when adding or removing a Domain in a forest.

Relative ID (RID) Master:

Allocates RIDs to DCs within a Domain. When an object such as a user, group or computer is created in AD it is given a SID. The SID consists of a Domain SID (which is the same for all SIDs created in the domain) and a RID which is unique to the Domain. When moving objects between domains you must start the move on the DC which is the RID master of the domain that currently holds the object.

PDC Emulator:

The PDC emulator acts as a Windows NT PDC for backwards compaitbility, it can process updates to a BDC. It is also responsible for time syncronising within a domain. It is also the password master (for want of a better term) for a domain. Any password change is replicated to the PDC emulator as soon as is practical. If a logon request fails due to a bad password the logon request is passed to the PDC emulator to check the password before rejecting the login request.

Infrastructure Master:

The infrastructure master is responsible for updating references from objects in its domain to objects in other domains. The global catalog is used to compare data as it recieves regular updates for all objects in all domains. Any change to user-group references are updated by the infrastructure master. For example if you rename or move a group member and the member is in a different domain from the group the group will temporarily appear not to contain that member.

There are five FSMO roles are two (Schema Master, Domain Naming Master) per forest, and three (RID Master, PDC Emulator, Infrastructure Master) in every Domain.

 

Flexible Single Master Operations

Operation Masters are Domain Controllers that play a specific roles. Other Domain Controllers are capable of playing that roles but do not at the same time.

AD DS contain five operation master roles,

Two forest wide Roles, these roles are must be unique in the forest. Each role is performed by only one domain controller in the forest.

1         Domain Naming Master

2         Schema Master

Three Domain Wide Roles: Each of these roles are performed by only one domain controller in the Domain

1         RID (Relative Identifier) Master

2         Infrastructure Master

3       PDC Emulator 

FSMO Stands for Flexible single Master operation and used For the smooth functioning of active directory and for efficeint administration of active directory we have5 FSMO Roles :1)Schema Master .2)Domian Naming Master3)Infrastructure Master4)RID Master5)PDC Emulator and Global Catlog.This roles are automatically installed when first domain controller is Installed.moreover this roles works automatically at backend without any human intervention until triggered by a system failure or during domain Migration

This roles can be easily moved or transferred from one server to another server in case of  system failure..

Flexible Single Master Operation Role

Schema Master

RID Master

Domain Naming Master

Infrastructure Master

PDC Emulator

When only on domain controller can perform specific Task that tssk ic called flexible single master operation.

Hope this little brief info helps you .

There are5 FSMO Roles (Flexible Single Master Operations)

1.       Schema Master

2.       Domain Naming Master

3.       PDC emulator

4.       RID Master

5.       Infrastructure master

Basically these roles can be assigned to individual servers for the balancing as each and every role has its own task. Hence instead of keeping all those roles with single server which leads to high load, traffic .It always better to keep it aside on different servers

ü  Schema Master and Domain Naming Master are “Forest wide Master Operations”

 

ü  PDC emulator, RID master and Infrastructure master are “Domain wide Master operation”

 

Well the most specific answer for these would be from none other than MIcrosoft themselves :) :

http://support.microsoft.com/kb/197132http://msdn.microsoft.com/en-us/library/cc223749.aspx