The IQNL-Series nodes cannot be upgraded to larger disk capacities.  With newer generation nodes (S200/X200/X400/NL400), a field upgrade is possible, however, it requires a Support engagement to update the serial-number-specific manifest file on each node to allow it to recognize its new configuration.
Wondering if it is even possbile to upgrade from 1TB drives in there IQ36NL nodes to 2TB drives? First off I would think this is technically possible but the question is, would we ever want to do it as i would be very messy and take a long time.  2 scenarios that I could see working listed in the order of ease of implementation from a conceptual standpoint. Performance is not a issue at this time on this cluster so creating hotspots although valid is not really a issue here.  I am just throwing this out there to see if anyone has even attempted this for my reference as the person I am working with told me that he was told that he could do this when the system was put in.
Drive upgrade in Existing Nodes