Upgrading the clients would be a lot less painful than attempting a regression, assuming you have run the nbpushdata command to bring all the media servers databases onto the new master?
I'm not certain that use of Vnetd is mandatory on NBU 6.xx.
You could ask Symantec if they have a de-conversion tool available for this regression?
Odd, You should be able to still use your old clients and they should use the same connection method.... Even so. To go back to 5.1MP4, you will need a copy of your old catalog tape from before the upgrade, and do a DR restore of your master. You probably will lose any backups you have done since the upgrade....
I have 51 clients on legacy 200+Nt boxes. They are running 4.5FP6.
This uses the old connection method rather than VNETD.
So i have entered them into the clients attributes section of master properties and set them to use the old connection settings.
When I run the backups individually or in small numbers they run fine.
When they all kick off I am getting issues of the ( for want of a better word ) supervisor job hanging and then I have to restart the services to get them to shut down.
I am suspicious that this is somthing to do with the number of available ports but am not sure.
Ahh! your clients are still 4.5... You can only go 1 major version down with your clients to a media server. In otherwards, if you upgraded your media servers to 6.0, your clients have to be at 5.0 or later. I know you can have a 6.0 master, with a 5.1 media server and 4.5 clients....
Not too hard, although I guess you would need to share the library with your 6.0 media server. Do you have Shared storage option? And you would have to update the client properties to allow the new server.