I understand now. I have some suggestion to look at. Its just odd that a process is giving you throughput issues.
Not sure how your monitoring your metrics on the Graylog server but I would be looking at the I/O on the disk, eth0, top/htop or perhaps using Wireshark.
I would check if there is another service/application running at the same time when the archiving process is running. Just trying to get any data and see what’s actually going on during the archiving.
Correct me if I’m wrong but your eth0 port is 10 Gbit/s? If this is correct you shouldn’t have any lag.
If not, and this is a throughput issue I would really look at you network and traffic. Have you checked your ESXi server network? I think you have some type of virtual switch on the servers. I would look into that also to insure your are getting your throughput.
Do you have switches and if so are you monitoring them for throughput when the archiving process is running?
I assume your checking all these when the archiving process is running.