Replication

This resource contains performance counters specific to the status of the current replication process. The icons of the listed performance counters in the Statistic Name column changes color to reflect the listed counter's current state. Clicking any performance counter in the Statistic Name column takes you to the Performance Counter Details page for that counter.

If the value of a listed performance counter approaches or crosses the Warning threshold, a yellow band will appear for the listed counter allowing plotted values that cross the threshold to easily be visualized against the yellow band. If the value of a listed performance counter approaches or crosses the Critical threshold, a red band will appear for the listed counter allowing plotted values that cross the threshold to easily be visualized against the red band. Hovering over any time period within the chart will display detailed information about that time period in the tooltip. Hovering over a counter will give you detailed information about that performance counter.

The purpose of using data replication is to maintain current replicas of the data. Exchange servers can use the replicas to provide continuity of email service in the event of a storage or site outage in the primary location.

The following table lists the default performance counters for this resource along with their respective definitions and troubleshooting information, including default Warning and Critical thresholds:

Counter Expert Knowledge Warn-
ing
Criti-
cal

CopyQueueLength

Definition:
Shows the number of transaction log files waiting to be copied to the passive copy log file folder. A copy isn't considered complete until it has been checked for corruption.

Information:
All nodes in a Database Availability Group (DAG) should be monitored for this counter depending on the passive node. Should be less than 1 at all times for continuous replication.

Possible problems:
Server recently rebooted or services restarted, network connectivity issues, or multiple mailbox moves are in process.

Remediation:
Verify network connectivity between the various nodes in the DAG. Verify Replication Service is running on all DAG members.

> 1

> 1 for 5 polls

ReplayQueueLength

Definition:
Shows the number of transaction log files waiting to be replayed into the passive copy. 

Information:
With DAG replication, transaction logs are shipped to the other DAG members. They then replay the log file. (Thresholds should be manually removed for DAG members configured to be 'lagged copies.')

Possible problems:
The replay queue length should be as low as possible, otherwise this could indicate a (performance) issue with the DAG member containing the Copy database. A high number could also
negatively affect failover with some loss of data as a possibility.

Remediation:
Check Memory, CPU, and Disk I/O for any bottlenecks. Review the Windows Event logs for any related events.

> 50 for 5 polls

> 100 for 5 polls

Avg Log Copy Latency (msec)

(Only available in Exchange 2010)

Definition: 
Average number of milliseconds observed by the log copier when sending messages over the network.

N/A

N/A

Log Copy KB/sec

Definition: 
The size of the log files (in KB) that are copied per second.

Information:
Shows the size in KB/sec of the transaction logs being copied to passive copies.

N/A

N/A 

Log Replay Rate (generations/sec)

Definition: 
The number of log files that have been replayed per second.

Information:
Shows you the number of Transaction Logs being replayed on the passive copies of a database.

N/A

N/A

Log Replay is Not Keeping Up

Definition: 
LogReplayNotKeepingUp is 1 when log replay is falling behind and not able to keep up with log copying and inspection.

Information:
Exchange 2010/2013 uses continuous replication to create and maintain database copies. To maintain a synchronized copy of a mailbox database, transaction log files from the active mailbox server are replayed into the passive database of another server in the DAG. This provides high availability and resiliency in the Exchange environment.

Possible problems:
Indicates a replication issue may exist with the mailbox database copies in the DAG. If Transaction Log replay is not able to keep up with the active copy, passive copies will not be up of date.

Remediation:
Review the Windows Event logs for any related events. Examine network topology between DAG members and verify connectivity and network latency is below 250 ms. Examine CPU utilization by the Information Store service on passive copies. Examine the replication status for each replica database using the Get-MailboxDatabaseCopyStatus cmdlet.

>= 1

 >= 1 for 60 polls

Zooming

You can have the chart show a predetermined time period of data by clicking on any one of the three Zoom buttons in the head of the Zoom column. Alternatively, you can have the chart show a specific date range by dragging the mouse over an area of the chart. The time and date displayed at the top of the resource shows the amount of data currently loaded into the chart. This can be changed by clicking Edit from within the resource.

The Value from Last Poll column shows the most recent data available for the listed statistic.

Additional components on certain resources may be available for addition and/or deletion on the Edit page.