Backup performance issues on vsphere 6.7 compared to 6.5

[JaySt]

We've got a case open with Veeam support, 03939298
I'm hoping for some extra insights regarding the issue.

We've upgraded from vsphere 6.5 to 6.7 latest and greatest. After the upgrade, we noticed the backup performance was about half of what it was before we did the upgrade.
We use NBD transport on 10Gbit. Storage is 10Gbit iSCSI Nimble Storage. No issues there.
After some troulbleshooting with support, we found out that when we backup the (fileserver) VM by adding the ESXi host directly within Veeam and selecting it through that host, the performance is at the level it was on 6.5. Only when we backup the VM by selecting the VM through the vCenter inventory tree, the backup performance is much worse (half). Support has done alot to find out why this happens. Tried every VDDK version available, but no changes in performance. digging into the network traffic, support found between every processed block there's a 0.005 second pause in processing when vCenter is used for VM selection. Full and incremental backups are both affected.

Weird behavior, not sure where to zoom in. It's not really infra related i think if performance is OK when going through the host directly. Not sure what vCenter has to do with this, but it somehow does.

Any ideas?

[Gostev]

I'm afraid not... 6.7 has been around for a very long time, and this issue was never brought up by other customers. So we can be reasonably sure this is an issue with the specific environment.

[JaySt]

how lucky i feel
we'll continue with support.
i was looking into some NFC connection limits/buffer values that changed through vsphere versions. I also found some text stating some things are not configurable within vCenter, where hostd on ESXi hosts is configurable. Maybe vCenter has lower limits/values (or enforces some of them during backup) compared to ESXi hosts.

https://vdc-repo.vmware.com/vmwb-reposi ... 0-00000364