When Veeam preferred networks cause slow backup initialization speeds

When using preferred networks in Veeam you choose to use another than the default host network for backups and restores. In this post, we’ll discuss how to optimize the Veeam preferred networks backup initialization speed because we aim for optimal performance. TL-DR: You need to provide connectivity to the preferred networks for the Veeam Backup & Replication server. It seems a common mistake I run into every now and then. Ultimately it makes people think Veeam is slow. No, it is just a configuration mistake.

Why use a preferred network?

Backups can fill up a 1Gbps pipe very fast. Many people still use 1Gbps networking as default connectivity to the hosts. Even when they leverage 10Gbps or better it is often in a converged network setup. This means that only part of the bandwidth goes to host connectivity. Few have 10Gbps for “just” host connectivity. This means it makes sense to select a different higher bandwidth network for backup and restore traffic.

Hence for high volume, high-performance backup and restores it is smart to look for a bigger pipe to leverage. Some environments have dedicated backup networks at 10Gbps or better. But we find way more high bandwidth networks for other purposes. In Hyper-V environments, you’ll have those for SMB networking like CSV, Live Migration variants and storage replication. Hyper-Converged Infrastructure deployments use these networks for storage as well. With S2D you’ll find more and more 25/50/100Gbps. All these can be leveraged as a preferred backup network in Veeam

Setting up a preferred network

Setting up a preferred network is easy. First of all, you figure out which network to use. You then add those to the preferred networks as follows:

In file menu select “Network Traffic Rules”

Click “Add” and specify the source IP as well as the target IP range. You can op to encrypt the traffic and /or set a bandwidth limit.

There is no need to have the preferred network registered in DNS. It will work fine without.

I hope it is clear that the source (Hyper-V Hosts), the target (backup repository or the extends in a Scale-Out Backup Repository) and any Off Host Proxies need connectivity to the preferred network(s). If you leverage WAN accelerators, Gateways Servers, log shipping servers than these also need access. Last but not least you should also make sure that the Veeam Backup Server (VBR) has access to the preferred networks. This is one that a lot of people seem to forget. May because it is most often a VM if it is not a shared role on the repository server or such and things do work without it.

When the VBR server has no access to the preferred networks things still work but initialization of the backup and restore jobs is a lot slower. Let’s test this.

Slow Initialization of backup and restore jobs

As a result of using preferred networks you might probably notice the following:

• First of all, we notice a slow down in the overall initialization of the backup and restore job.
• This manifests itself in a slow start of the actual VM backup/restore and reducing the number of simultaneous backups/restores of VMs within a job.

Without the VBR server having connectivity to the preferred networks

Optimize the Veeam preferred networks backup initialization speed

With the VBR server having connectivity to the preferred networks. Notice how smooth and continuous the throughput is.

When you look into the Veeam backup logs for this job you will find at various stages attempts by the VBR server to connect to the preferred networks. If it can’t it has to wait until it times out. You see entries like:

A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.10.110.2:2509 (System.Net.Sockets.SocketException)

This happens for every file in the backups (config files and disks) for every extend in the Scale-Out Backup Repository (per VM backup chain). This slows down the entire backup job tremendously.

Conclusion

I always make sure that the VBR servers in my environments have preferred network connectivity. Consequently, initialization is faster for both backups and restores. Test it out for yourself! It is the first thing I check when people complain of really slow backup. Do they have preferred networks set up? Check if the VBR server has connectivity to them!