Long Fat Networks

[Sumico]

Does anyone have experience dealing with backups over long fat networks (LFNs)? If so, how did you optimize Veeam to take full advantage of the bandwidth. We are currently running into a problem on a 1Gb link with a latency of 19ms. We are using Veeam 6.0 and ESXi 4.1.

[tsightler]

I don't know if I would consider 19ms particularly long, but it may be enough to keep the defaults from achieving maximum throughput if that's the "problem" you are having.

Ideally you still need a proxy on both sides (or proxy on one side and repository on the other if it's backups as opposed to replication). Then you'll want to tune the number of TCP connections used between the proxies. To do this you can add the following registry key to the Veeam server:

Code: Select all

DownloadStreamsNumber
DWORD

You can then change the number of TCP streams used to optimize bandwidth on the connection. It's hard to know exactly where to start, but the default is 5 connections, so as an example, if you're seeing 250Mb with the default settings, then try 20 streams and see if that helps. If you get no improvement, then something else is going on. For one customer with a similar issue (1Gb, ~45ms latency) we found that 25 streams worked great.

[Sumico]

Thanks.

My problem is that the link is being underutilized.

Where is that registry key?

[tsightler]

Sorry, you'll need to add it to the Veeam Server in the following registry path:

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HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Backup and Replication

You can verify it's working with netstat by looking at the number of TCP connections between VeeamAgents, or with a tool like TCPView.

[Gostev]

This settings has been moved into the user interface in 7.0.

[yizhar]

Thanks.
My problem is that the link is being underutilized.

OK, but how did you check if the link is underutilized because of networking or other stuff?

Can you post results from a sample backup job (a full backup job is best for that test, vs incremental).

Yizhar

[Yukinobu]

Does this registry key value have max limit?

[foggy]

I don't think the question is in the limit for the discussed setting itself but rather in the number of streams that allows to saturate your link, which, I suppose, can be derived from actual testing only (as depends on such factors as link latency and network hardware settings).

[veremin]

In fact, the maximum limit is dictated by memory size. One stream requires approximately 3MB of RAM at each side. Thanks.

[Gostev]

Potentially, there can be further limitations dictated by the networking hardware. This is certainly not common, but I've personally witnessed once when the following connection attempts through the router would fail after reaching certain amount of connections. Then, as some existing connections were closing, new connections in place of them were opening fine.

[Yukinobu]

Thanks.
This setting is no limit, but has environment limit.