Flexible single master operation

Flexible Single Master Operations (FSMO, F is sometimes floating ; pronounced Fiz-mo), or just single master operation or operations master, is a feature of Microsoft's Active Directory (AD).[1] As of 2005, the term FSMO has been deprecated in favor of operations masters.

FSMO is a specialized domain controller (DC) set of tasks, used where standard data transfer and update methods are inadequate. AD normally relies on multiple peer DCs, each with a copy of the AD database, being synchronized by multi-master replication. The tasks which are not suited to multi-master replication, and are viable only with a single-master database, are the FSMOs.[2]

Contents

Description of FSMO Roles

One per Microsoft Windows Server Domain

These roles are applicable at the domain level

  1. Password changes performed by other DCs in the domain are replicated preferentially to the PDC emulator.
  2. Authentication failures that occur at a given DC in a domain because of an incorrect password are forwarded to the PDC emulator before a bad password failure message is reported to the user.
  3. Account lockout is processed on the PDC emulator.
  4. Backwards compatibility: the PDC emulator performs all of the functionality that a Microsoft Windows NT 4.0 Server-based PDC or earlier PDC performs for Windows NT 4.0-based or earlier clients.

One per Microsoft Windows Forest of Domains

These roles are unique at enterprise level

Moving FSMO Roles Between Domain Controllers

By default AD assigns all operations master roles to the first DC created in a forest. If new domains are created in the forest, the first DC in a new domain holds all of the domain-wide FSMO roles. This is not a satisfactory position. Microsoft recommends the careful division of FSMO roles, with standby DCs ready to take over each role. When a FSMO role is transferred to a different DC, the original FSMO holder and the new FSMO holder communicate to ensure no data is lost during the transfer. If the original FSMO holder experienced an unrecoverable failure, you can force another DC to seize the lost roles; however, there is a risk of data loss because of the lack of communications. If you seize an FSMO role instead of transferring the role, that domain controller can never be allowed to host that FSMO role again,except for the PDC emulator Master operation and the Infrastructure Master Operation. Corruption can occur within Active Directory. FSMO roles can be easily moved between DCs using the AD snap-ins to the MMC or using ntdsutil which is a command line based tool.[3]

Certain FSMO roles depend on the DC being a Global Catalog (GC) server as well. For example, the Infrastructure Master role must not be housed on a domain controller which also houses a copy of the global catalog in a multi-domain forest (unless all domain controllers in the domain are also global catalog servers), while the Domain Naming Master role should be housed on a DC which is also a GC. When a Forest is initially created, the first Domain Controller is a Global Catalog server by default. The Global Catalog provides several functions. The GC stores object data information, manages queries of these data objects and their attributes as well as provides data to allow network logon.

The PDC emulator and the RID master should be on the same DC, if possible. The Schema Master and Domain Naming Master should also be on the same DC. To provide fault tolerance, there should be at least 2 domain controllers available within each domain of the Forest. Furthermore, the Infrastructure Master role holder should not also be a Global Catalog Server, as the combination of these two roles on the same host will cause unexpected (and potentially damaging) behaviour in a multi-domain environment.[4]

Active Directory support tools

Note: These tools are not restricted to FSMO administration.

Several additional tools that can be used to configure, manage, and debug Active Directory are available as command-line tools.[5] These tools are known as the Support Tools and are available on the installation CD in the \Support\Tools folder.

List and description of tools

In addition, the Active Directory Migration Tool (ADMT)[6] is available to help you migrate user accounts, groups, and computer accounts from Windows NT 4.0 domains to Active Directory domains. The Active Directory Migration Tool is a Microsoft Management Console (MMC) snap-in and is available on the installation compact disk in the \i386\ADMT folder.

Tool Description

Global Catalog

Note: The Global Catalog task is not restricted to a single host within a domain or forest. It is not a FSMO task.

The Global Catalog (GC) contains an entry for every object in an enterprise forest but only a few properties for each object.[7] An entire forest shares a Global Catalog, with multiple servers holding copies. You can perform an enterprise wide forest search only on the properties in the GC, whereas you can search for any property in a user’s domain tree. Only Directory Services (DS) or Domain Controller (DC) can hold a copy of the GC.

Configuring an excessive number of GCs in a domain wastes network bandwidth during replication. One GC server per domain in each physical location is sufficient. Windows NT sets servers as GCs as necessary, so you don’t need to configure additional GCs unless you notice slow query response times.

Because full searches involve querying the whole domain tree rather than the GC, grouping the enterprise into one tree will improve your searches. Thus, you can search for items not in the GC.

By default, the first DC in the First Domain in the First Tree in the AD Forest (the root domain) will be configured as the GC.

You can configure another DC to become the GC, or even add it as another GC while keeping the first default one. Reasons for such an action might be the need to place a GC in each AD Site. To configure a Windows 2000/2003 Domain Controller as a GC server, perform the following steps:

Start the Microsoft Management Console (MMC) Active Directory Sites and Services Manager. (From the Start menu, select Programs, Administrative Tools, Active Directory Sites and Services Manager).

Select the Sites branch. Select the site that owns the server, and expand the Servers branch. Select the server you want to configure. Right-click NTDS Settings, and select Properties. Select or clear the Global Catalog Server checkbox, which the Screen shows. Click Apply, OK.

You must allow for the GC to replicate itself throughout the forest. This process might take anywhere between 10–15 minutes to even several days, all depending on your AD infrastructure.

References

  1. ^ http://www.petri.co.il/understanding_fsmo_roles_in_ad.htm
  2. ^ "Windows 2000 Active Directory FSMO roles". Microsoft Corporation. 2007-02-23. http://support.microsoft.com/kb/197132/en-us. "To prevent conflicting updates in Windows 2000, the Active Directory performs updates to certain objects in a single-master fashion. [...] Because an Active Directory role is not bound to a single DC, it is referred to as a Flexible Single Master Operation (FSMO) role." 
  3. ^ http://support.microsoft.com/kb/255504
  4. ^ http://support.microsoft.com/kb/248047
  5. ^ http://technet.microsoft.com/en-us/library/cc782713%28WS.10%29.aspx
  6. ^ http://www.microsoft.com/downloads/details.aspx?familyid=B1F816C0-4E2B-4E5D-B256-1AC304062367&displaylang=en
  7. ^ http://technet.microsoft.com/en-us/library/cc728188%28WS.10%29.aspx

http://support.microsoft.com/kb/324801