Hope this may help you

http://seer.entsupport.symantec.com/docs/279049.htm

Not really :-(

If I add a new server Media can i have more spaces for my backup ? so how can i see this ? in Storage Units ?

Please give us more info about your current config:
Was the DAS used for NetBackup catalogs or for disk based backups (or both)?
If catalogs are filling up the space, it won't help to add a media server.
There are ways to move catalogs to new storage (different methods for Windows and Unix).
If DAS volumes are utilized by disk backups, adding a media server with it's own storage will help.
The media server will be able to backup network clients, sharing the load with the master server (or take over the actual backup function, which leaves the master to control, configure, schedule, store catalogs, etc).
Do you have the necessary license keys to add another server?

Ok thanks for your answer !
My configuration:
1 Master Backup Server HP Proliant DL 580 G2 with attached to a HP MSA
Now the storage on the MSA and and the server is full.
All port (SCSI) behind my Master server are full.
The das is used for both catalog and disk based backup.
My catalog size is just 10 Gb.
I don't have actualy necessary licence for another server but I  can without problem buy a new one.

So what do you mean ?

Next year we change all the server and we buy a san storage but I need a tempory solution.

A temporary solution will be to add more storage to your current server. Can the storage on your HP MSA be increased?  Not the best solution, but you can also consider adding a network mapped drive and create a new storage unit for that.
Are you not relocating the disk storage to tape? (Disk staging)
If you only have disk storage for backups, were multiple backups with multiple retention levels taken into account?

If a media server will not be part of your future design, it is not advisable to add one as a temporary solution. It will just add unnecessary complexity when it needs to be merged again into a single server solution.

No the HP MSA Storage is full we don't increased it.
Yes we make disk staging but the Librairy is full too.
I don't can use the media server for have more space ?