## 3.1 Modules and drives 

IBM FlashSystem can contain three types of internal storage: NVMe FlashCore Modules (FCM), NVMe flash drives, and SAS flash drives. The system is all-flash, spinning drives are not supported and can’t be installed to its control or expansion enclosures. However, FS9100 can be clustered with Storwize V7000 family machines, which support them. 

## 3.1.1 NVMe storage 

FlashSystem 9100 control enclosure has 24 x 2.5” slots to populate with NVMe storage. 

## NVMe protocol 

NVM Express (NVMe) is an optimized, high-performance scalable host controller interface designed to address the needs of systems that utilize PCI Express-based solid-state storage. The NVMe protocol is an interface specification for communicating with storage devices. It is functionally analogous to other protocols, such as SAS. However, the NVMe interface was designed for extremely fast storage media, such as flash-based solid-state drives (SSDs) and low-latency non-volatile storage technologies. 

NVMe storage devices are typically directly attached to a host system over a PCI Express (PCIe) bus. That is, the NVMe controller is contained in the storage device itself, alleviating the need for an additional I/O controller between the CPU and the storage device. This architecture results in lower latency, throughput scalability, and simpler system designs. 

NVMe protocol supports multiple I/O queues, versus legacy SAS and SATA protocols that use only a single queue. 

According to Fibre Channel Industry Association (FCIA) publications as a result of the simplicity, parallelism and efficiently of NVMe, it delivers significant performance gains versus SCSI, such as: 

GLYPH<SM590000> For 100% random reads, NVMe has 3x better IOPS than 12 Gbps SAS 

GLYPH<SM590000> For 100% random writes, NVMe has 1.5x better IOPS than 12 Gbps SAS 

GLYPH<SM590000> For 100% sequential reads: NVMe has 2x higher throughput than 12 Gbps SAS 

GLYPH<SM590000> For 100% sequential writes: NVMe has 2.5x higher throughput than 12 Gbps SAS 

In addition to just IOPS and throughput, the efficiencies of the command structure of NVMe also reduce CPU cycles by half, as well as reduce latency by more than 200 microseconds compared to 12 Gbps SAS. 

## Industry-standard NVMe drives 

FS9100 provides an option to use self-encrypting industry-standard NVMe flash drives, which are available with capacity from 1.92 TB to 15.36 TB. 

Supported NVMe SSD drives are built in 2.5-inch form factor (SFF) and use a dual-port PCIe Gen3 x4 interface to connect to the midplane. 

## NVMe FlashCore modules 

At the heart of the IBM FlashSystem system is IBM FlashCore technology. IBM FlashCore Modules (FCMs) are a family of high-performance flash drives, that provide performance-neutral, hardware-based data compression and self-encryption. 

The current generation of FCMs is built with 64-layer 3D TLC NAND flash technology and Everspin MRAM cache in 2.5-inch U.2 form factor drive. 

