Adding volumes Equilogic Vmware ESXi 4.1

Hi ....

We have a dell Equilogic SAN PS4000e, with 2 Esxi hosts

The setup was made by a consultant 2 years ago...

He made 5 volumes on the SAN...

Now i want to add more volumes (we have 2.3 TB free in the SAN)

I have read the documentation for the SAN about adding volumes but feel a bit insecure.

This system is running 24/7 and I dont want it to malfunction in any way....

Is it something I should take in to consideration regarding adding the volumes to our vmware environment?

Regards 

Kbergros