The XtremIO X2 storage system can be expanded for capacity (Scale-Up) or both capacity and performance (Scale-Out). The system begins with a single building block, called an X-Brick, with a minimum of 18 SSDs. When additional capacity is required, the system scales up, with up to 72 SSDs for a single X-Brick1. Therefore, to upgrade a single X-Brick XtremIO X2 cluster that already contains 36 SSDs, the minimum number of SSDs required would be 18, which is the base configuration for an X-Brick.