How to check for performance or network problems in ESXi to ESXi backups

Backups between two ESXi servers are not performing as expected or there are network issues

Solution

Procedure to transfer data manually between two ESXi servers:
1.In VM Explorer disable the scheduler and check that no backups are running at the moment
2.Using vSphere Client connect to the server SourceServer and create a snapshot of the VM exampleVM.
3.In the same vSphere Client select the tab "Configuration", under "Security Profile", and click the "Properties..." link at the right of "Firewall
4.In the new window ensure that "SSH Client" is enabled
5.Using vSphere Client connect to the server TargetServer and repeat steps 3 and 4
6.Using a SSH client connect to the SourceServer (SourceServerIP)
7.Execute the command: scp "/vmfs/volumes/<SourceDatastore>/<SourceVMFolder>/<SourceDisk-flat.vmdk>" <TargetAdminUsername>@<TargetServerIP>:"'/vmfs/volumes/<DatastoreName>/tempFile.tmp'"

SCP command output will show the average transfer speed
We can use this to establish a performance baseline
Also if there are any disconnections SCP will report them

Please note that when using Windows you can also use free software that will grant the same possibility:
http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
PSCP works similar to SCP on a Windows system