Applies to: Exchange Server 2013, Exchange Online
Topic Last Modified: 2012-10-13
In Microsoft Exchange Server 2013, Exchange workloads are throttled based on the health of specific system resources. When specific system resources reach unhealthy levels, Exchange uses a configurable classification system based on policy settings to make sure that each Exchange workload is able to consume the appropriate amount of system resources. This topic contains information about the Exchange workloads and system resource thresholds.
Exchange workloads are managed by default workload management policy settings that are installed during Exchange Server 2013 Setup. You can make global changes to the default settings that apply to all the servers in your organization. You can also make changes to workload management settings on specific servers in your organization. For more information, see Exchange Workload Management.
Contents
Terminology
Knowledge of the following terms will help you understand the information referenced in this topic.
- Exchange workload
-
An Exchange workload is an Exchange server feature, protocol, or service that has been explicitly defined for the purposes of Exchange system resource management. Each Exchange workload consumes system resources such as CPU, mailbox database operations, or Active Directory requests, to run user requests or background work. Examples of Exchange workloads include Outlook Web App, Exchange ActiveSync, mailbox migration, and Managed Folder Assistant.
- Workload classification
-
A workload classification specifies the default priority of each Exchange workload. A workload can be assigned one of the following classifications: Urgent, Customer Expectation, Internal Maintenance, and Discretionary.
- System resource health indicator
-
A system resource health indicator is used to measure the health of a specific component on an Exchange server. The system resource health indicators that have been defined for the purposes of Exchange system resource management include CPU, mailbox RPC latency, and mailbox replication latency. Exchange workloads are throttled based on one or more of the available system health indicators.
- System resource thresholds
-
A system resource threshold represents a configurable limit for a system resource. Each Exchange workload classification has three different configurable thresholds. The thresholds define the underloaded, overloaded, and critical levels for each system resource.
Exchange workloads and classifications
The following table shows the default Exchange 2013 workload policies and the default classification for each workload. To review the default threshold value for each system resource health indicator based on workload classification, see the section “System resource thresholds”.
 Note: |
|---|
You can view the workload policies and workload classifications
that are currently set up in your environment using the Exchange
Management Shell. To review the values for all Exchange 2013
workloads, from the Shell, run
Get-WorkloadPolicy. |
The following are the Exchange workloads and their default classifications.
| Workload policy name | Description | Workload classification |
|---|---|---|
|
MailboxReplicationServiceHighPriority |
Mailbox Replication service high priority |
Urgent |
|
Eas |
Exchange ActiveSync |
Customer expectation |
|
JunkEmailOptionsCommitterAssistant |
Junk email |
Customer expectation |
|
PowerShellBackSync |
Windows PowerShell BackSync operations |
Customer expectation |
|
PowerShellForwardSync |
Windows PowerShell FwdSync operations |
Customer expectation |
|
PublicFolderMailboxSync |
Public folder mailbox synchronization |
Customer expectation |
|
TeamMailboxSync |
Site mailbox synchronization |
Customer expectation |
|
Transport |
Transport mail flow |
Customer expectation |
|
CalendarRepairAssistant |
Calendar Repair Assistant |
Internal maintenance |
|
CalendarSyncAssistant |
Calendar Synchronization Assistant |
Internal maintenance |
|
ContactLinkingAssistant |
Contact Linking Assistant |
Internal maintenance |
|
DirectoryProcessorAssistant |
Directory Processor Assistant |
Internal maintenance |
|
Domt |
Address book |
Internal maintenance |
|
ELCAssistant |
Managed Folder Assistant |
Internal maintenance |
|
Ews |
Exchange Web Services |
Internal maintenance |
|
Imap |
IMAP4 |
Internal maintenance |
|
Momt |
RPC Client Access and Outlook |
Internal maintenance |
|
OABGeneratorAssistant |
Offline Address Book Generation Assistant |
Internal maintenance |
|
OrgContactsSyncAssistant |
Organizational Contacts Synchronization Assistant |
Internal maintenance |
|
Owa |
Outlook Web App |
Internal maintenance |
|
OwaVoice |
Outlook Web App Voice Access |
Internal maintenance |
|
PeopleRelevanceAssistant |
People Relevance Assistant |
Internal maintenance |
|
Pop |
POP3 |
Internal maintenance |
|
PowerShell |
Windows PowerShell work that’s not included in the other Windows PowerShell workloads |
Internal maintenance |
|
PowerShellGalSync |
Windows PowerShell work related to global address list synchronization |
Internal maintenance |
|
PowerShellLowPriorityWorkFlow |
Windows PowerShell work that’s generally not time sensitive |
Internal maintenance |
|
PushNotificationService |
Push Notification service |
Internal maintenance |
|
SharingPolicyAssistant |
Sharing Policy Assistant |
Internal maintenance |
|
SiteMailboxAssistant |
Site Mailbox Assistant |
Internal maintenance |
|
StoreMaintenanceAssistant |
Store maintenance |
Internal maintenance |
|
TopNAssistant |
Top N Words Assistant |
Internal maintenance |
|
TransportSync |
Transport synchronization |
Internal maintenance |
|
UMReportingAssistant |
Unified Messaging Reporting Assistant |
Internal maintenance |
|
InferenceDataCollectionAssistant |
Inference Data Collection Assistant |
Discretionary |
|
InferenceTrainingAssistant |
Inference Training Assistant |
Discretionary |
|
MailboxReplicationService |
Mailbox Replication service |
Discretionary |
|
PowerShellDiscretionaryWorkFlow |
Windows PowerShell work that’s generally not time sensitive |
Discretionary |
|
PublicFolderAssistant |
Public folders |
Discretionary |
Default system resource thresholds
The following tables show the default thresholds for each of the five system resources that are used to throttle Exchange workloads. Three thresholds (underloaded, overloaded, and critical) are defined for each system resource. The thresholds that apply to a system resource depend on the workload classification assigned to the workload (workload classifications include: discretionary, internal maintenance, customer expectation, and urgent).
| Note: |
|---|
You can view the system resource threshold settings that are
currently set up in your environment using the Exchange Management
Shell. To review the Exchange 2013 threshold values, from the
Shell, run Get-ResourcePolicy | format-list. |
The following are the system resources and their default thresholds.
Local Server CPU (Processor)
| Workload classification | Threshold | Percent |
|---|---|---|
|
Discretionary |
Underloaded |
70 |
|
Discretionary |
Overloaded |
80 |
|
Discretionary |
Critical |
100 |
|
Internal Maintenance |
Underloaded |
75 |
|
Internal Maintenance |
Overloaded |
85 |
|
Internal Maintenance |
Critical |
100 |
|
Customer Expectation |
Underloaded |
80 |
|
Customer Expectation |
Overloaded |
90 |
|
Customer Expectation |
Critical |
100 |
|
Urgent |
Underloaded |
100 |
|
Urgent |
Overloaded |
100 |
|
Urgent |
Critical |
100 |
Mailbox Database RPC Latency (MDBLatency)
| Workload classification | Threshold | Milliseconds |
|---|---|---|
|
Discretionary |
Underloaded |
10 |
|
Discretionary |
Overloaded |
20 |
|
Discretionary |
Critical |
70 |
|
Internal Maintenance |
Underloaded |
10 |
|
Internal Maintenance |
Overloaded |
20 |
|
Internal Maintenance |
Critical |
70 |
|
Customer Expectation |
Underloaded |
15 |
|
Customer Expectation |
Overloaded |
30 |
|
Customer Expectation |
Critical |
70 |
|
Urgent |
Underloaded |
25 |
|
Urgent |
Overloaded |
50 |
|
Urgent |
Critical |
100 |
Mailbox Database Replication Health (MdbReplication)
| Workload classification | Threshold | Bytes |
|---|---|---|
|
Discretionary |
Underloaded |
2097152 |
|
Discretionary |
Overloaded |
3145728 |
|
Discretionary |
Critical |
6291456 |
|
Internal Maintenance |
Underloaded |
2097152 |
|
Internal Maintenance |
Overloaded |
3145728 |
|
Internal Maintenance |
Critical |
7340032 |
|
Customer Expectation |
Underloaded |
2097152 |
|
Customer Expectation |
Overloaded |
3145728 |
|
Customer Expectation |
Critical |
8388608 |
|
Urgent |
Underloaded |
2097152 |
|
Urgent |
Overloaded |
3145728 |
|
Urgent |
Critical |
9437184 |
Content Indexing Age of Last Notification (CiAgeOfLastNotification)
| Workload classification | Threshold | Seconds |
|---|---|---|
|
Discretionary |
Underloaded |
10 |
|
Discretionary |
Overloaded |
15 |
|
Discretionary |
Critical |
180 |
|
Internal Maintenance |
Underloaded |
10 |
|
Internal Maintenance |
Overloaded |
15 |
|
Internal Maintenance |
Critical |
180 |
|
Customer Expectation |
Underloaded |
10 |
|
Customer Expectation |
Overloaded |
15 |
|
Customer Expectation |
Critical |
180 |
|
Urgent |
Underloaded |
10 |
|
Urgent |
Overloaded |
15 |
|
Urgent |
Critical |
180 |
Content Indexing Retry Queue Size (CiRetryQueueSize)
| Workload classification | Threshold | Items |
|---|---|---|
|
Discretionary |
Underloaded |
540 |
|
Discretionary |
Overloaded |
1080 |
|
Discretionary |
Critical |
2700 |
|
Internal Maintenance |
Underloaded |
540 |
|
Internal Maintenance |
Overloaded |
1080 |
|
Internal Maintenance |
Critical |
2700 |
|
Customer Expectation |
Underloaded |
540 |
|
Customer Expectation |
Overloaded |
1080 |
|
Customer Expectation |
Critical |
2700 |
|
Urgent |
Underloaded |
540 |
|
Urgent |
Overloaded |
1080 |
|
Urgent |
Critical |
2700 |
Mailbox Database Availability Health (MdbAvailability)
| Workload classification | Threshold | Bytes |
|---|---|---|
|
Discretionary |
Underloaded |
2097152 |
|
Discretionary |
Overloaded |
3145728 |
|
Discretionary |
Critical |
6291456 |
|
Internal Maintenance |
Underloaded |
2097152 |
|
Internal Maintenance |
Overloaded |
3145728 |
|
Internal Maintenance |
Critical |
7340032 |
|
Customer Expectation |
Underloaded |
2097152 |
|
Customer Expectation |
Overloaded |
3145728 |
|
Customer Expectation |
Critical |
8388608 |
|
Urgent |
Underloaded |
2097152 |
|
Urgent |
Overloaded |
3145728 |
|
Urgent |
Critical |
9437184 |