The HPE Alletra 5000 is a hybrid storage array family built on the legacy of the HPE Nimble Storage Adaptive Flash architecture. Its hardware design is optimized for a mixture of high-capacity Hard Disk Drives (HDDs) and high-performance Solid State Drives (SSDs) used for caching (CASL architecture).

The chassis is a 4U enclosure featuring 24 drive slots. To maintain consistent performance and thermal profiles, the architecture designates specific slots for different media types. According to the HPE Alletra 5000 Installation and Service Guide, the SSDs used for cache are housed in Dual Flash Carriers (DFC). Each DFC can hold either one or two SSDs, allowing for a total of 3 or 6 cache drives per shelf. These DFCs are specifically required to be installed in the last three slots of the array, which are slots 22, 23, and 24. The remaining 21 slots (slots 1 through 21) are populated with Large Form Factor (LFF) HDDs for the primary capacity tier.

Option B is incorrect because the system is flexible; it can be configured with a minimum of 3 SSDs (one in each DFC) and does not require the maximum of 6. Option C is incorrect because expansion shelves (like the HPE Alletra 2120) also support their own cache SSDs, meaning the "entire system" capacity for SSDs scales as shelves are added. Option D is incorrect because the Alletra 5000 is a SAS/SATA-based hybrid platform; it does not support NVMe SSDs in its drive slots. NVMe support is reserved for the all-flash Alletra 6000 and 9000 models. Understanding this physical slotting is crucial for site planning and field service operations to ensure the array initializes correctly.