How to Increase ASR (Azure Site Recovery) Replication and Failback Default Settings

Now that you have deployed ASR (Azure Site Recovery), for Hyper-V and have started to up being replication, you notice the replication process just might take forever, as there are several VMs still queued. That is right, by default, ASR will replicate 4 (four) VMs at a given time. This value can be increased (to a maximum of 32), however, where to change this setting?

In order to increase the number of replication threads from 4 to 32, or whatever in between, you first need to launch the Registry and navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Azure Backup\Replication

From there, you will need to create the key, if the key does not exist (I have never see it by default in any of my deployments…). Create the key, “UploadThreadsPerVM” and set its value to whatever you see fit. Again, the maximum is 32.

Likewise, you can increase the default (4) number of threads used for data transfer during failback. This value represents the maximum number of VMs that will failback from ASR. That path is the same, and the Registry Key is,”DownloadThreadsPerVM“, and again, can be set to a maximum of 32.

After that is completed, your Hyper-V Registry Keys, would look something like this. Please note, this change is fully supported by the ASR/Microsoft team. However, do note, this change can saturate your network due to the increase in uploads to Azure. You can also increase and change the schedule for the bandwidth throttle settings, you can see that previous post here, see Step 10.


For additional information on this, please visit,

One thought on “How to Increase ASR (Azure Site Recovery) Replication and Failback Default Settings

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s