The base enclosure is an all-NVMe platform, capable of supporting NVMe SSD, NVMe SCM, and NVMe NVRAM drives. You can populate slots 0 through 20 with NVMe SSD or NVMe SCM drives. Slots 21 through 24 are reserved for NVMe NVRAM drives which serve as additional system write caching. PowerStore 1000 and PowerStore 3000 models contain two NVMe NVRAM drives in slots 23 and 24.