Hello Tradsd, Ah that would be your issue. Yes both the drives need to be the same size & speed otherwise the pool will use the specs of the smallest drives to build the pool. Yes you can expand the pool live as you will just need to get the drives seen by MDSM and as long as they are showing as unassigned then you can assign them to any disk pool or disk group that you want to. Here is a link to the administrator guide & if you look on page 97 it explains about drives with the same physical size. ftp://ftp.dell.com/Manuals/Common/powervault-md3200_Administrator%20Guide_en-us.pdf  Please let us know if you have any other questions.
I have an MD3220 with a 1220 shelf and I'm trying to re-configure and create one large disk pool with all 48 disks.  However, when I go to create the disk pool, it only pulls 24 disks in for 14tb but shows 32tb available.  I blew away the configuration of the previous setup because we had to take a 1220 shelf from this unused array for another project so now I am getting back around to reconfiguring.  I'm wondering if the premium features need to be re-enabled because I cleared the config.  Possibly that is it.  When I go to md-storage.com to regenerate a key of course it does not have any idea what my system is.  Is there something I am missing.   Should be a two minute task which is now going to take hours apparently.
Only 24 of 48 disks available for Disk Pool