System Center Data Protection Manager 2007: TCP Chimney and Bandwidth throttling

December 22, 2009 at 3:22 pm in Uncategorized by mikeresseler

Hey All,

I’ve seen a number of cases where the backup of hyper-v guests is failing and also where the backup is extremely slow.  Almost every time, some small adjustments need to be made to fix them, but if you are not the network administrator or hardware administrator, this can cause a lot of discussions.

Suppose you have a DPM server with all the latest patches till date, a hyper-v host and some virtual machines.  You are of course also backing up other stuff from other servers.  You notice that your hyper-v guests are failing (the consistency check is running but never ends, file backups take a lot of time and so on…)

For the hyper-v guests backup, make sure that you check the TCP Chimney Offloading in windows.  When this is enabled on the host drive, it doesn’t always work.  I don’t know why but when I disabled it (both on the DPM server and on the hyper-v host) the backup ran without any problems.

The command to do that is netsh int tcp set global chimney=disabled

Now that the backups are running, the speed isn’t still optimal.  I read somewhere (but I can’t remember where and can’t find it back) that you sometimes need to enable bandwidth throttling.  I did that, gave it a huge number (it was off after all…) and after that we saw a huge increase in backup speed.

One doesn’t always have to do with the other but when you are experiencing failed backups or slow backups, it is certainly worth the try by disabling the TCP Chimney Offloading and enable the bandwidth throttling.  It might save your day :-)



PS: If you want more information on TCP Chimney, visit