Backup Performance drops down during backup
I do have a question regarding a Backup Exec 2012 SP3 Installation on Windows 2008 R2 backing up a VMware installation with vSphere 5.1 latest using SAN transport mode on a dedicated iSCSI environment using a EMC VNX with 1-GBit iSCSI on two switches with two isolated subnets to an internal hard drive RAID5 array configured as a dedupe store.
What actually happens now is, that a GRT job starts with a very good performance about 80% of the available network bandwidth but after a while you can see in the network monitor that the bandwidth drops down to 2-6% all of a sudden and does not recover back to a satisfying speed. The job keeps running on that speed till the end what means, that a VM with a TB or more data runs for days.
Anyone here who had or has the same issues?
I first encountered that problem with BE2012 and it keeps showing up till now. Changing the job back to LAN transport starts with the usual 25% of the available network speed but stays there till the end. One strange thing is, that using SAN transport mode with no GRT directly to a SAS tape loader works fine.
Any help would be really appreciated.