I have a doubt about the creating the disk staging unit
I got 5TB disk ( which is my D drive ) . Is it recommended or possible to create the multiple disk storage unit pointing the same drive (directly pointing the D drive-absolute path for storage )-All the disk storage units i am planning to use for the basic staging purpose
I think you should split your 5Tb LUN into, say, 5 1Tb ones and then create a separate DSSU against each LUN. Next, as you got your brand-new DSSUs, you should create a storage unit group and add these DSSUs into that storage unit group. Symantec recommends "round-robbin" priority for that sort of storage unit groups. Finally, you configure backup policies with storage unit group as a backup destination and voila you have fault-tolerant D2D2T solution. It is should be mentioned that the best practice is to spread multiple DSSUs across a numberof media servers to prevent media server failure.
Do NOT mix multiple staging storage units on the same drive. Here's why...
When you're backing to say dssu1, you will likely eventually hit the highwater mark. At this point, NetBackup will attempt to clean up space by deleting the staged images, but it will ONLY look at dssu1. It will not look at dssu2 even though it is on the same volume. So let's say you have a highwater mark at 80% (4TB). You have 3.5TB in dssu2 and 200GB in dssu1 and it's all been destaged already. You start a backup job that will require 1TB for dssu1. There is no way to complete this job because NetBackup doesn't have enough space and won't clean it up in dssu1.
There is a technote on this as well but the short answer is do not do this.