Thank you very much.That is the info I needed.
I will talk to centera support on the details.

Based on the info which you provided, you have the Gen4 version of the product which had 1.2TB raw capacity per node. Current product available [please check with your account team for details] is the Gen4LP which has 4TB raw capacity per node. A two node addition will provide 4TB [less overhead] of useable space.

When adding capacity there is no need to set aside additional space. The reserved space is performed on a cube basis. Therefore you will be able to add 12 more nodes w/o incurring any additional overhead.

The capacity can be added online. For Clusters running CentraStar version 3.1.3 and 4.x the nodes will auto upgrade [or downgrade] to the cluster sealed version.

Then adding new hardware there are minimum CentraStar version requirements.
Please review your current configuration with your account team to also determine if a upgrade is required before adding the new hardware. Currently nodes are added in quanties [multiples] of 2. The latest available nodes have a raw capacity of 4TB each.

GB, Thank you for the info.

So, if I need to add 1.2 TB of usable space, how big of raw capacity should that be and how many nodes? Currently, in a 4 node cluster, this is what I have:

Total Raw Capacity: 4,769 GB (100%)
Used Raw Capacity: 2,625 GB (55%)
Free Raw Capacity: 2,144 GB (45%)