That definitely helps. I had a feeling this was the reality but wanted to make sure before I look into adding another shelf.

Thanks a lot!

No - you can not add any disk drive to the Bottom enclosure which has plastic fillers on the front.

This is actually the Data Mover enclosure - which contains the Data movers (you get the cge ports at the back of the data movers) - and no disk can be used on this enclosure. Even you forcefully add a disk here - it will not be usable at all.

The NS500 Data mover enclosure used to have the same chasis as a CX500 Disk processor enclosure (Storage processors at the back and disks at the front) - so when the same chasis is used for Data mover enclosure - the data movers are in the place of SPs - and thus leaving the front side open. Many by mistake assume that disks can be inserted here - but that's not true.

So - the configuration you have will be represented as

DAE (disk array enclosure) - on the top - with 15x146 GB drives
NS500-AUX (CX500 DPE) - in the middle - with SPs and Flare disks
NS500 - DME (Data Mover Enclosure) ---- at the bottom

In fact there are two more units in the middle - the NAS control station and the CX500 SPS (battery) enclosure).

So - if you don't have any space left in the currently configured storage pools even after some cleanup - you may have to buy new Disk enclosure.

Hope this helps,
Regards,
Sandip