Traffic Control not working as described on the help page (or the description is misleading)

[yummiweb]

Proxmox Backup Server 4.1.6

Traffic Control not working as described on the help page (or the description is misleading)

According to the help page:

https://mypbs:8007/docs/network-management.html#sysadmin-traffic-control
"Traffic Control" is not active for "Sync Jobs":

Quote:

"Note - Sync jobs on the server are not affected by the configured rate limits. If you want to limit the incoming traffic of pull-based or outgoing traffic of push-based sync jobs, you need to set up a job-specific rate-in limit. See Sync Jobs."

I created traffic policies (without consulting this help page) to better control the traffic between two PBSs (based on time) – and I thought the traffic was responding to them, but I haven't actually tested it. Later, I checked the help page and was somewhat surprised by the aforementioned limitation (Sync jobs on the server are not affected… …you need to set up a job-specific rate-in limit). Therefore, I actually tested "Traffic Control," and it seems that, contrary to the instructions, "Traffic Control" does indeed react to "Sync Jobs" between different PBSs.

I tested it with a remotely started pull job (remote PBS), which definitely reacted to a significantly reduced local "Traffic Control" rate. Initially, the traffic bar in the Sync Job list (Rate Out) showed a value well over 100%, and then the traffic rate immediately dropped to the set value (measured on the network device). After changing the local traffic rate, the traffic immediately increased again.

Is the function faulty, or are the instructions outdated or poorly written?

Or does the description mean: "Only sync jobs started on the local PBS are not included in the rating, while remotely started sync jobs (like mine) are included?" This isn't explicitly excluded in the description, but it's not mentioned either. (Such a distinction doesn't make much sense to me.)

I like the current behavior, but I'd like to be able to rely on it not being "fixed" later and then no longer working.

Regards, Yummiweb

 

[d.oishi]

I think this is less a feature bug and more a documentation issue.

"Traffic Control" does indeed react to "Sync Jobs" between different PBSs.

Based on the following forum post, this behavior appears to be intended:

[SOLVED] Post in thread 'PUSH SYNC Limit no works'

Mar 10, 2025

No, what I meant is that since the PBS sync job acts like a backup job for the remote target, you can set the rate limit on the target PBS instance. The burst was just out of interest in case you had a value that would allow for an initially higher throughput.

• Chris

 

[yummiweb]

Thank you for pointing this out.

However, the "clarification" there makes it even more unclear, in my opinion. I quote:

Yes, that is what I intended with setting the rate limit on the target PBS. That is a valid workaround to apply the rate limit (if you have access to the remote).

In my case, it's exactly the opposite.

The source PBS is pulled by the target PBS. And the sync reacts to the traffic rate set by the traffic control on the source PBS.

"Setting the rate limit on the target PBS" also seems to be imprecisely worded. Because in my case, the rate limit is set at the source.

Perhaps the behavior should be understood as follows: the criterion isn't source or destination, but rather the perspective from which the sync is initiated. Therefore, the rate limit must be set on the PBS that responds to the sync, not on the PBS that initiates the sync.