When backing up VMs using a VMware layer backup software like Veeam, the network disconnects momentarily. This is because the software tells VMware to take a snapshot of the VM, which causes a decrease in the number of IOPS available, which results in the VM dropping the network connection.
This is normal behaviour and will cause about a packet to be lost. If the VM’s network disconnects for more than a second, then you may have a storage performance issue. There may be a few configuration options available in your backup software to reduce the amount of snapshots being taken, therefore reducing the IOPS strain on the datastore and reducing the duration of the network disconnection. These might include:
- Setting only one backup to occur at a time
- Moving effected VMs to datastores with more available IOPS
- Backing up at times when there are fewer IOPS on datastores
- In the case of VMs with multiple disks, split the disks between multiple datastores to reduce IOPS
- Use DRS Rules to put the backup appliance on the same ESXi host as the VMs it’s backing up
Basically, anything to reduce the number of IOPS on the datastore the VM is on, will reduce the period of the network disconnection.