Are you using Oracle Enterprise Manager to monitor the exadata? if yes , you can use it to monitor the storage on exadata.
Sorry for the late reply, but for the community, its never late. You can use cellcli with dcli tool to retrieve the cell specifications, example;
dcli -g /root/cell_group -l root "cellcli -e list griddisk detail"
dcli -g /root/cell_group -l root "cellcli -e list celldisk detail"
Where cell_group is a text file containing all your storage node's hostname, seperated by newline;
# cat cell_group
To follow-up on what Nishant wrote above in the thread, here are some resources you may be interested in researching for monitoring Exadata with Enterprise Manager:
Enterprise Manager Oracle Exadata Database Machine Getting Started Guide
Enterprise Manager Exadata Management
Exadata Health and Resource Usage Monitoring
Hope this helps.