Buschini Edouard wrote:

1: Can you add more storage?

I can but I would like to do some clean up before. Add space disk

move temporarily the issue :(

The issue is how long you need to keep backups

2: Why not use tape?

I don't know when I arrived in the company it has already been designed like
that : Dell server with 15kSAS raid10

(IMHO)

That's insane for backups.

You don't need small expensive high speed disks in an inefficient raid10 layout for backups, you need lots of large slow ones in raid6 (or on ZFS, XFS, etc), and for spooling you should use SSDs if you can afford them (but you don't need to spool if writing to disk only...)

An autochanger is less expensive than you might think and LTO tapes are rated for at least 10 years - which takes care of regulatory requirements in most countries if you fall into that field.