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Using Network Bandwidth Usage Throttling

Published : September 27, 2005

Network bandwidth usage throttling limits the amount of network bandwidth that DPM can use to create and synchronize replicas. Throttling helps to ensure that network bandwidth is available to applications other than DPM.

The advantage of using network bandwidth usage throttling is that it enables you to limit the amount of network resources a synchronization job can consume. The disadvantage of network bandwidth usage throttling is that it can lengthen the amount of time each synchronization job takes to complete.

Network bandwidth usage throttling is configured for each protection group. Set network bandwidth usage throttling in terms of an absolute maximum of data to be transferred per second. For example, if you establish a limit of 50% of a 512 Kbps connection, the file servers in that protection group will send data at a rate no greater than 256 Kbps.

Figure 3.2 shows the dialog box that you use to enable network bandwidth usage throttling.

Figure 3.2   Modify Protection Options Dialog Box

Although you use a percentage to configure network bandwidth usage throttling, the limit that is applied is the value of that percentage at the time that it is set, and the limit does not change dynamically when connection speeds change. In the example of 50% of a 512 Kbps connection, the network bandwidth usage throttling limit is 256 Kbps. If this connection is later upgraded to 100 Mbps, the network bandwidth usage throttling limit remains 256 Kbps.

Use the following guidelines to select network connection speed:

  • If the speed of your network connections is not listed in the menu, select the connection speed listed that is closest to the actual speed.

  • If the speed of your network connections is midway between two connection speeds in the menu, select the slower speed.

Network bandwidth usage can be limited by Group Policy also. The Group Policy reservable bandwidth limit on the local computer determines the combined reservable bandwidth for all programs that use the Packet Scheduler, including DPM. The DPM network bandwidth usage limit determines the amount of network bandwidth that DPM can consume during replica creation, synchronization, and consistency checks. If the DPM bandwidth usage limit, either by itself or in combination with the limits of other programs, exceeds the Group Policy reservable bandwidth limit, the DPM bandwidth usage limit may not be applied.

For example, if a DPM computer with a 1 gigabits per second (Gbps) network connection has a Group Policy reservable bandwidth limit of 20 percent, 200 Mbps of bandwidth is reserved for all programs that use the Packet Scheduler. If DPM bandwidth usage is then set to a maximum of 150 Mbps while Internet Information Services (IIS) bandwidth usage is set to a maximum of 100 Mbps, the combined bandwidth usage limits of DPM and IIS exceed the Group Policy reservable bandwidth limit, and the DPM limit may not be applied.

To resolve this issue, reduce the DPM setting for maximum network bandwidth usage. For more information, see “How to modify protection options” (http://go.microsoft.com/fwlink/?linkid=51911) in DPM Help.

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