We have an F740 with 3 shelves of 18GB disks. It's config'd as two volumes (two raid sets). We've almost outgrown the capacity (we're down to one hot spare and a free disk).

We want to add a new disk shelf to the system, but we're wondering if we're going to lose anything by going to a shelf of 36gb disks. We don't have any intention of adding new volumes (or new raid sets), just growing the existing volumes.

Can we add a shelf of 36gb disks and then switch our 2 existing 18gb parity disks over to 36gb disks? We'd keep a 36gb disk as a hot spare and use all of the 18gb disks in the volumes (including the 2 freed up parity disks and the freed up hot spare). Are we going to run into problems with this? Or do we need to keep an 18gb disk around as a hot spare as well (ie when an 18gb disks dies and uses a 36gb disks as a hot spare, can we force it to go back to the 18gb disk once the faulty 18gb disk has been replaced?).

Are the 36gb disks going to be used at full capacity in this situation (when mixed with the 18gb)? Or is there a better way to do this?

Thanks,