Refer primus article "emc198527" which clearly explains you......
We have an NX4 with an AX4 backend.  I would like to add a new disk enclosure which is populated with 12 600GB SAS disks.  Is this something that can be done hot, while users are accessing the system?  Or does the whole infrastructure need to be brought down (then a maint window)?  If it can be done hot, which is the best procedure to connect it.  Data cables first, then power cables second, or vice versa?  NX4 software revision is 6.0.51-6 The AX4 backend's are running FLARE 02.23.050.5.709   Thanks!
Can I add a new disk enclosure hot (no downtime)