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Summary


There are situations where throttling the data transfer of a Block backup client is necessary. This is typically desired when the client and storage servers are separated by a low bandwidth link. This KB article describes methods to configure the client to throttle outbound traffic, with particular emphasis on new DPX product functionality to help control data transfer.

 

 

Step By Step


Windows 2008 R2 and later has the built-in capability to define QoS networking rules on a per-process or per-IP-address basis. It is recommended to use this method for traffic throttling when possible. For details, see How to configure network Traffic Throttling with Windows. However, note that Windows group policy QoS settings are not compatible with the DPX product enhancement indicated below.

 

 

 

 

Requirements and Limitations:

 

  1. A Windows 2003 client must have QoS packet scheduler service installed. Since the installation may cause a brief network outage, schedule network maintenance time to install the service. A reboot is not required. Windows 2008 and later installs QoS by default. 

    The traffic.dll library needs to be on the system path, typically c:\windows\system32. The library is installed by default on both Windows 2003 and Windows 2008 based on Microsoft's installation instructions for QoS packet schedule service:
    technet.microsoft.com/en-us/library/cc782652%28v=WS.10%29.aspx
    technet.microsoft.com/en-us/library/bb870370(v=office.12).aspx
  2. Install WMI packages on Windows 2003 clients. You can use WMIC from a CMD command shell to automatically install the necessary WMI packages.
  3. Use only one form of node throttling, either Windows QoS, Job throttling, or the new throttle option for Advanced backup jobs. Attempting to mix throttle methods will not result in predictable performance, and may result in much lower performance than expected.
  4. The actual sent throughput may be more than the throttle value, within a certain tolerance range.
  5. When the DPX client attempts to set throttling and the operating system reports a failure, the Block job fails. The administrator may either remove node throttling to continue the backup or correct the throttling configuration issues to proceed with the backup. This failure condition is expected, because insufficient throttling may cause unexpected network bandwidth use across restricted WAN links.
  6. The Block transmission rate is capped by the throttle value set on the client. The node throttle is host-based; that is, the throttle is independent of the number of concurrent backup jobs or tasks.

 

Configuring the DPX node throttle option:

  1. Run Regedit on the Windows client machine.
  2. Drill down into HKLM\Software\Syncsort\BackupExpress\<node-name>\0, where <node-name> is the name of the local/client machine.
  3. Create a new string value as follows:

    NIB_NODE_THROTTLEKBS RG_SZ <kb/s val>

    where <kb/s val> is the kilobyte per second transfer rate to throttle. For example, for 10mb/s define this value to be 10240.
  4. Close Regedit.
  5. Restart the Advanced Protection Manager Windows service