We have discussed the "cost" of replication over a particular site link, but how can we really know the impact of replication traffic on network bandwidth and server performance? Windows 2000 provides tools for monitoring replication traffic to give you precise values on which to base replication configuration decisions.
Viewing Replication Traffic
System Monitor (also called Performance Monitor): Measures replication coming in and going out of a specific server
Replication Monitor: To view your intra-site replication topology
In NT, the System Monitor tool was called Performance Monitor, BUT in the Administrative Tools menu in Windows 2000, it is still listed as "Performance. This is a common source of confusion for many administrators transitioning from NT to Windows Server.
Using the Performance console
The replication counters in the Performance console measure the size and efficiency of Active Directory replication traffic.
To open the Performance console, click Performance in the Administrative Tools menu. The image below shows the Performance console when it is first opened.
Reviewing the Directory Replication Agent Counters
Once opened, the Performance console gives you access to several Directory Replication Agent (DRA) counters.
The DRA counters are found under the NTDS performance object.
Some commonly used counters include the following:
DRA Inbound Bytes Total Since Boot.
Shows total number of bytes inbound.
Sum of the number of uncompressed bytes (those that are never compressed) and the number of compressed bytes (after compression).
DRA Inbound Bytes Not Compressed (Within Site) Since Boot.
Shows number of inbound bytes replicated, which were not compressed at the source.
This means they were replicated from other Directory System Agents (DSAs) within the same site.
DRA Inbound Bytes Compressed (Between Sites, Before Compression) Since Boot.
Shows original size in bytes of inbound compressed replication data.
DRA Inbound Bytes Compressed (Between Sites, After Compression) Since Boot.
Shows compressed size in bytes of inbound compressed replication data.
DRA Outbound Bytes Not Compressed (Within Site) Since Boot.
Shows number of bytes replicated out that were not compressed.
This typically implies they were sent to DSAs within the same site, or that less than 50,000 bytes of replicated data was sent.
A (REPLMon) Replication Monitor is a command-line utility that you install with the Windows 2000 Support Tools on the Windows 2000 compact disc. Replication Monitor displays the replication topology of connections between servers. It enables administrators to view low-level status and performance of replication between Active Directory domain controllers. It also includes functions that are wrapped application programming interfaces (APIs) which make it easy to script replication with just a few lines of code.
Replication tasks using Active Directory
With Active Directory Replication Monitor you can accomplish a variety of tasks:
Display the servers participating in the replication, both directly and transitively. Replication Monitor includes a Server Wizard that allows you to browse for the server to monitor. With Server Wizard, you can also create an .ini file that specifies the names of servers to be monitored, which will be loaded by the Replication Monitor.
Display each Update Sequence Number (USN) value, the number of failed attempts, the reason for failure, and flags used for direct replication partners.
Poll the server at an administrator-defined interval to get current statistics and replication state, and keep a log file history.
Monitor the count of failed replication attempts. If the failure rate meets or exceeds an administrator-defined value, it can write to the event log and send mail.
Administrator replication tasks using Active Directory
The Active Directory Replication Monitor allows administrators to:
show which objects have not yet replicated from a particular machine
synchronize between just two domain controllers
trigger the KCC into recalculating the replication topology
The Replication Monitor utility can be run on any domain controller, member server, or stand-alone computer running Windows Server.
In the next lesson, we will wrap up this module.