Yep it’s certainly possible. Once your virtual disk is extended from a RAID controller perspective then (assuming you’ve hardened your server) you’d reboot into single user mode and extend the disk from an Ubuntu perspective.

Yep...should be able to using sudo growpart /dev/sd# command. Then don’t forget to resize your filesystem as well: sudo resize2fs /dev/sd# . You can then verify your additional storage size: sudo parted /dev/sd# print free 

Hope that helps!

if I got that right - just add the disks the physical server then enters the Array Configuration Utility and select the RAID 5 we did and expand it with the new disks ? 
and restart the server than expand the repository volume in Ubuntu and rescan in Veeam?

without break the existing RAID 

Yep that’s the long short of it as @coolsport00 said don’t forget to extend the file system too!

Yes...that should do it. I’d review HPE documentation on extending your RAID in the ACU though just so you’re following proper procedures.

thank you all for your answers.