Database Input and Output

This resource contains performance counters specific to the status of database I/O. The icons of the listed performance counters in the Statistic Name column change colors 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 performance counter.

If the value of a listed performance counter crosses the Warning threshold, the chart for the listed counter displays a yellow background. If the value of a listed monitor crosses the Critical threshold, the chart for the listed counter displays a red background. Hovering over any time period within the chart displays detailed information about that time period in the tooltip. Hovering over a counter gives you detailed information about that performance counter.

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

I/O Database Reads Average Latency

Definition:
Shows the average length of time, in ms, per database read operation.

Information: 
Should be 20 ms on average. Spikes should not exceed 50 ms.

Possible problems:
Users may experience decreased performance, including delayed message deliveries.

Remediation:
If the disk subsystem is not meeting demand, correcting the problem may require additional disks, faster disks, or modifying the disk configuration. Review the event logs for related events. Verify network topology between mailbox servers and storage resources. Examine CPU & Memory usage to determine possible bottlenecks. Examine replication status for replica database.

> 50 ms

> 50 ms for 5 polls

I/O Database Writes Average Latency

Definition:
Shows the average length of time, in ms, per database write operation.

Information: 
Should be 50 ms on average. Spikes of up to 100 ms are acceptable if not accompanied by database page fault stalls.

Possible problems:
Users may experience decreased performance, including delayed message deliveries.

Remediation:
If the disk subsystem is not meeting demand, correcting the problem may require additional disks, faster disks, or modifying the disk configuration. Review the event logs for related events. Verify network topology between mailbox servers & storage resources. Examine CPU and Memory usage to determine possible bottlenecks. Examine replication status for replica database.

> 100 ms

> 100 ms for 5 polls

I/O Log Reads Average Latency

Definition:
Indicates the average time, in ms, to read data from a log file. Specific to log replay and database recovery operations.

Information:
Average should be less than 200 ms with spikes up to 1,000 ms

Possible problems:
Users may experience decreased performance, including delayed message deliveries.

Remediation: If the disk subsystem is not meeting demand, correcting the problem may require additional disks, faster disks, or modifying the disk configuration. Review the event logs for related events. Verify network topology between mailbox servers & storage resources. Examine CPU and Memory usage to determine possible bottlenecks. Examine replication status for replica database.

> 200 ms

> 200 ms for 5 polls 

I/O Log Writes Average Latency

Definition:
Indicates the average time, in ms, to write a log buffer to the active log file.

Information:
This count should be 10 ms or less on production servers.

Possible problems:  
Indication that the Exchange Database\I/O Database Writes Average Latency is too high

Remediation: If the disk subsystem is not meeting demand, correcting the problem may require additional disks, faster disks, or modifying the disk configuration. Review the event logs for related events. Verify network topology between mailbox servers & storage resources. Examine CPU and Memory usage to determine possible bottlenecks. Examine replication status for replica database.

> 10 ms

> 10 ms for 5 polls

Log Threads Waiting

Definition:
Shows the number of threads waiting for their data to be written to the log to complete an update of the database. If this number is too high, the log may be in a bottleneck situation.

Information: 
Should be less than 10 on average.

Possible problems: 
If this number is too high, the log may be a bottleneck. Regular spikes concurrent with log record stall spikes indicate that the transaction log disks are in a bottleneck situation. If the value for log threads waiting is more than the spindles available for the logs, there is a bottleneck on the log disks.

Remediation:
If the disk subsystem is not meeting demand, correcting the problem may require additional disks, faster disks, or modifying the disk configuration. Review the event logs for related events. Verify network topology between mailbox servers and storage resources. Examine CPU and Memory usage to determine possible bottlenecks.

> 10 for 5 polls

> 10 for 15 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.