Massive inbound traffic when backing up server
On one of our cPanel servers we're seeing massive inbound traffic (6x more than outbound) whenever a backup is running.
In the attached screenshots you can see a daily graph (blue is outbound, green is inbound), where you can see the amount of traffic I'm talking about and for how many hours it's going on.
I have also attached a yearly graph where you can see the difference of in/out traffic since we switched from R1Soft to Acronis in December. Same server, same amount of data and backup frequency, but a huge difference in the bandwidth bill.
What's weird is that every backup run for this server takes almost 3 hours. Backups on this (and other servers) is configured to run every 7 hours, but this is the only server were so much traffic is exchanged.
And I'm very certain that there's not that much difference in the filesystem between every backup run, that could cause such an amount of traffic to be exchanged. Other server with similar amount of data (~600GB) take ~15 minutes for the backup run to complete.
This server is running the same backup plan as the other servers that are not experiencing this.
What can I do to further investigate what all this data is, and why it's taking so long for the incremental backups to finish?