After trial and error, I found that a sub-folder with 4000 files and only 1 GB in size.
But backup will take forever to complete. I have to cancel the job as it takes more than 10 hrs. I can see that the number of files are increasing albeit very slowly.
I tried adv client with snapshot. BUt it seems the same.
Have you tried to do a raw partition backup instead? This backs up the partition and isn't affected by the high number of I/O's associated w/ many (millions) of files. The only drawback is that when you restore, you have to restore the entire partition- you aren't able to restore an individual file.
You can change this policy by simply changing the backup selections properties. The syntax for the entry is "/\\.\DRIVE_LETTER:" (without the quotes). So, for example, to backup the Z: drive you would enter /\\.\Z: in the selection list.
First, Let's try VSS or VSP or disable "Open File Backup".
Second, In order to investigate the cause which backup does not complete, please set up bpbkar, bpbrm and bptm(bpdm) debug log (or bpfis, bpfilter, bpcd, bpdbm, etc) and check them.
By the way, has the problem occurred in both NBU6.0 and 6.5?