HP MSA2312sa G2 RAID Controller Replacement

[Justin-F]

I have recently noticed that 1 of 2 RAID controllers on a HP MSA2312sa G2 Modular Smart Array has failed.  Everything failed over to Controller A which is still healthy so all is still up and running. 

However my question is whether I can hot swap the failed RAID controller with a new one or if I have to shut the unit and all attached hosts down to do the hardware replacement.

Any help is appreciated as this is a one off device that I don't have much experience with.

Thanks

Justin