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70-294: MCSE Guide to Microsoft Windows Server 2003 Active Directory, Enhanced Chapter 4: Active Directory Architecture. Objectives. Describe the underlying database of Active Directory Describe the Active Directory schema and how it can be extended
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70-294: MCSE Guide to Microsoft Windows Server 2003 Active Directory, EnhancedChapter 4: Active Directory Architecture
Objectives • Describe the underlying database of Active Directory • Describe the Active Directory schema and how it can be extended • Describe the different Active Directory partitions and their functions
Active Directory Physical Database Storage • Layers • Provide the directory service • Include: • Extensible Storage Engine (ESE) • Database layer • Directory Service Agent (DSA)
Active Directory Physical Database Storage • Extensible Storage Engine: • Lowest level • Directly responsible for manipulating database • All objects stored in nonhierarchical form • Rows in database table • Database layer: • Responsible for providing object-oriented hierarchical view • Directory Service Agent: • Third layer • Responsible for enforcing rules • Govern how objects in Active Directory are created and manipulated • Only adjacent layers communicate with one another
Extensible Storage Engine • Active Directory store: • Transactional database • Transaction • Each addition, modification, or deletion • Needed data is loaded from disk to memory.
Extensible Storage Engine (continued) • Example: Viewing properties of a user account • ESE loads data user account data form disk to memory. • Transaction • Operation is logged to hard disk (First thing that happens) • Modification transaction performs made to the in-memory copy of data • Manipulating in-memory copy of data is faster that going to disk
Extensible Storage Engine (continued) • AD store can be many gigabytes in size. • Storing entire database in memory is not practical because of finite amount of memory available • To solve this issue, ESE uses a Least recently used algorithm to write to disk (Data that has not been accessed or modified recently is the first to be written back to disk.) • Move data that is no longer needed • Write changes back to hard drive • When memory is running low • System is at a period of low activity
Extensible Storage Engine (continued) • (In case of driver crashers, UPS failure) • Transactions: • ESE writes all transactions to log before they are made to in-memory copy • Next time domain controller starts, ESE can use transactions recorded in log • Reapply changes to copy of data stored on hard disk • Called recovering the database • Done without user intervention
Extensible Storage Engine (continued) • Checkpoints: • Shorten recovery times • Reduce amount of hard drive space logs take up • Completed transactions written back to disk • Fact that transactions were successfully written is noted • ESE only needs to reapply transactions from point of last checkpoint • Transactions can be deleted from log • Note: • Shutdown of domain controller creates a checkpoint in transaction log. • When server is started ESE check log, if no checkpoint present, a recovery is performed.
Active Directory File Structure • Files needed by ESE to maintain Active Directory Store integrity: • NTDS.DIT • EDB.LOG • EDBXXXXX.LOG • EDB.CHK • RES1.LOG and RES2.LOG • TEMP.EDB
NTDS.DIT • This is the main AD database. • NTDS stands for NT Directory Services. • The DIT stands for Directory Information Tree. • Stores all objects and their attributes • Located in %SYSTEMROOT%\ NTDS folder on domain controllers • Made up of three tables: • Schema table • Data table • Link table
EDB.LOG • This is a transaction log. • Any changes made to objects in Active Directory are first saved to a transaction log. • During lulls in CPU activity, the database engine commits the transactions into the main Ntds.dit database. • This ensures that the database can be recovered in the event of a system crash. • Entries that have not been committed to Ntds.dit are kept in memory to improve performance. • Transaction log files used by the ESE engine are always 10MB.
EDBXXXXX.LOG • Auxiliary transaction logs used to store changes if the main Edb.log file gets full before it can be flushed to Ntds.dit. • When EDB.LOG is filled, it is renamed to EDBXXXXX.LOG • The original Edb.log file is renamed to Edb00001.log, and EdbXXXXX.log is renamed to Edb.log file, and the process starts over again. • Excess log files are deleted after they have been committed. • Every 12 hours: • Garbage-collection process runs • Deletes old EDBXXXXX.LOG • You may see more than one Edbxxxxx.log file if a busy domain controller has many updates pending.
EDB.CHK • This is a Checkpoint file • It is used by the transaction logging system to mark the point at which updates are transferred from the log files to Ntds.dit. • System recovering from failure • As transactions are committed, the checkpoint moves forward in the EDB.CHK file. If the system terminates abnormally, the pointer tells the system how far along a given set of commits had progressed before the termination. • .
RES1.LOG and RES2.LOG • These are reserve log files. • If domain controller runs out of free disk space, uses reserved space from files • Prevents updates from being lost due to insufficient disk space • The system then puts a dire warning on the screen prompting you to take action to free up disk space quickly before Active Directory gets corrupted. • You should never let a volume containing Active Directory files get even close to being full. • Important: • Include additional free space to store Active Directory database as it grows
TEMP.EDB • Temporary storage space • Hold large transactions while they are in process • Used during maintenance operations
LDAP • When Microsoft decided to replace the clumsy Registry-based account management system in classic NT with a true directory service, rather than devise a proprietary directory service of their own, they chose to adopt LDAP. • Lightweight Directory Access Protocol • Primary protocols for accessing information directories. • Vital to understand how to use LDAP naming paths
LDAP (continued) • DN (Distinguished Name) • Every object in Active Directory has unique name • Describes exactly where the object is located in the object hierarchy • Made up of: • Name of the object • All of parent objects above it in hierarchy
LDAP (continued) • RDN (Relative Distinguished Name) • Identifies object within its container • Contains only name of object • Acronyms for object names: • DC (Domain Component) • Part of a domain name • OU (Organizational Unit) • Name of an organizational unit • CN (Common Name) • Name of most objects
LDAP (continued) • Name example: • Lori Thompson located in dev.supercorp.net domain in Research organizational unit • DN: • CN=Lori Thompson • OU=Research • DC=dev, DC=supercorp, DC=net • RDN: CN=Lori Thompson
Active Directory Schema • All available objects and attributes • Sets out exactly: • What kind of objects are represented • What properties or attributes are required or optional • What types of values are acceptable • Tool needed to modify the schema is not available by default (regsvr32 schmmgmt.dll)
Activity 4-1: Registering Active Directory Schema Console • Objective: Register the Active Directory Schema snap-in so you can view and modify the schema • Follow instructions to register the console
Naming • Every object class and attribute in the schema must have: • Unique common name • LDAP display name • Object Identifier (OID)
Common Name Rules • Start name with registered DNS name of company • Separate each level of DNS name with hyphens (-) instead of periods • Add another hyphen (-) at end of company’s name • Enter current year • Follow year with another hyphen (-)
Common Name Rules (continued) • Choose product-specific prefix • Must be unique within company • Identifies product or application of class or attribute • Should begin with uppercase letter with additional letters using capitalization of your choice • Follow product-specific prefix with hyphen (-) • Enter name of class or attribute separated by hyphens
LDAP Display Name Rules • Start with common name already created for class or attribute • Make first character of product-specific prefix lowercase • Characters following first character may be uppercase or lowercase
LDAP Display Name Rules (continued) • Make every character in class or attribute part of name that is preceded by a hyphen (-) uppercase • Remove all hyphens (-) after product-specific prefix
OID • OID space must be obtained separately • Not part of registered DNS domain name • Two primary ways to obtain an OID space: • Through Microsoft • International Standards Organization (ISO)
Object Classes • Definition of each type of object • Like a template from which objects are created • Inheritance • Class Types: • Structural classes • Abstract classes • Auxiliary classes • 88 classes
Object Classes (continued) • Possible superiors • Controls which types of objects new object can be instantiated or moved under • Example: user object cannot be created (or moved) under a printer object
Activity 4-2: Creating a Structural Class • Objective: Learn how to extend the Active Directory schema to include additional classes • Use Active Directory Schema to create a new class
Attributes • Schema contains list of all possible attributes • Class is assigned both mandatory and optional attributes • Object is sum of its attributes • Syntaxes • Defines data type attribute can store
Indexes • Similar in concept to index in back of book • Store values (in order) for all objects that have a given attribute • Speed up queries • Slow down creation of objects and updating of attributes • Choose attributes that have highly unique values
Activity 4-4: Adding an Optional Attribute to a Class • Objective: Learn how to add additional attributes to a class • Use the Schema console to add an attribute to a class
Active Directory Partitions • Database divided into groups called partitions, or naming contexts • Used to manage replication • Partitions: • Schema partition • Domain partition • Configuration partition • Application partition
Active Directory Partitions (continued) • ADSI Edit: • Included with Windows Server 2003 Support Tools • Used to view and modify objects in various Active Directory partitions
Schema • Stores schema • Contains definitions of all classes and attributes in entire forest • Replicated to all domain controllers in forest • Content is the same throughout forest
Configuration • Stores information about replication topology used in forest • Specifies how domain controller determines with which other specific partners it replicates • Found on all domain controllers • Same throughout forest
Domain • Contains users, computers, groups, and organizational units created in Windows domain • Replicated to all domain controllers in domain • Large amount of data • Usually partition that changes most frequently
Application • Cannot contain security principals • Can be replicated to many different domains in forest • Without necessarily being included on all domain controllers • Used when developer wants to store information in Active Directory
Summary • Active Directory is made up of several layers: • Extensible Storage Engine (ESE), • Database layer • Directory Service Agent (DSA) • By logging all transactions, ESE can reapply transactions in event of system failure and bring data back to a consistent state
Summary (continued) • All objects and attributes available in Active Directory are defined in Active Directory schema • To effectively manage replication of Active Directory, database is divided into groups called partitions