The virtual machine slows down during backup.

[Maksimus]

The virtual machine slows down during backup.

At the time of the first backup (backup on PBSv2), wild brakes begin on the virtual machine (during subsequent backups, such a problem was not noticed) as if the machine abruptly ended up on an old slow Pentium4 computer with a wild HDD at 5400 rpm on which something is constantly written.
But at the same time, the logs from zabbix do not show a critically large load on the disk.
At first they sinned on the network, but the network was loaded by 80-85% at the time of backup.
The disks are worth no load on the disks.
Tell me where to look?

 

[dcsapak]

i guess this is the way the backup works, when it's started, any pending write from inside the guest to a block that is not yet backed up, the write is blocked, backed up and only then allowed to continue. so if your backup speed is drastically lower (or higher latency) than your storage, this can happen. on subsequent backups, not the whole disks must be backed up, so this is probably less noticeable