So further testing done. to rule out an issue with the Cluster nodes and underlying compellent storage ive migrated our exchange server to a standalone host, the host has been added to the Veeam backup infrastructure. New backup job created for our exchange server that is on the standalone host with direct attached storage. Host is dual CPU 24 cores, 192 GB RAM, 24 x 146GB 15k disks so its by no means slow and the only VM is the exchange server.
Start the new backup job, snapshot process starts, pauses experienced in outlook, there are always 2 pauses as well. So the exact same behaviour on a standalone host.
Next test, our veeam platform sits behind a Virtual PFSense firewall which segregates it from our cloud platform so to rule the Pf Sense out of the equation ive multi-honed the B&R and Repo servers so they now sit in the cloud platform and can talk directly between the two without touching the virtual firewall. Again backup tested and the pause is experienced exactly as before.
In addition to the above i have also changed settings within the B&R server as per Veeams support request, so Storage Latency control enabled and set to 10ms on both settings, Max concurrent snapshots set to 1 on all volumes, Max tasks on the On Host Proxy's set to the default of 4.
Again ran the backup with all of the above settings reduced as well as the B&R and the Repo in their new configuration as well as the old configuration with no change what so ever, we still get the pause.
According to this article https://www.veeam.com/kb1896
The cause of the pause can be caused by Hyper-V 2012 R2 using a saved state backup if Online backup is not available, The saved state backup process causes the system up-time counter in Hyper-V manager to reset, which we are seeing, why we are seeing it i have not the foggiest idea or how to find out why its doing it and how to stop it doing it.
completely out of ideas now with this one. Anyone have any good suggestions as to where to look to try and resolve this will be appreciated