Overview for PCIe storage enclosures

PCI Express (PCIe) storage enclosures provide additional storage capacity to the system in the form of hard disk drives (HDDs) or solid-state drives (SSDs).

PCIe storage enclosures are connected to the system with PCIe cables. The PCIe cables extend the PCIe buses that are generated by PCI host bridges in the system, and transport PCIe protocol information and data between the system and the storage controllers in the PCIe storage enclosure.

Each PCIe cable connects to a PCIe connector on the system unit. The connector can be on a pluggable card, such as a PCIe GX++ adapter, or can be mounted directly on the system unit chassis. In either case, the connector is wired to a PCI host bridge that controls the PCIe protocol. The other end of the cable connects to a PCIe connector on the PCIe storage enclosure that is wired to a storage controller in the PCIe storage enclosure.

The PCIe interconnection between a system and a PCIe storage enclosure is point to point. Although a PCIe storage enclosure is connected to the system unit with two PCIe cables, there is no redundancy or cable failover capability in the PCIe links. However, access to all drives in the PCIe storage enclosure is maintained in the event of a single PCIe link failure because of the dual controllers and fully redundant SAS fabric within the PCIe storage enclosure.

Furthermore, there are multiple ways to connect the two PCIe cables from a PCIe storage enclosure to the system, some of which result in a better high availability characteristics than others. For example, connecting the two PCIe cables from a PCIe storage enclosure to different PCIe GX++ adapters in the system creates a more highly available configuration than connecting the cables to the same PCIe GX++ adapter. If the PCIe GX++ adapters are in different processor drawers, such as is possible with multi-drawer mid-range systems, such as 9117-MMC and 9179-MHC, the configuration is even more highly available.

With proper software support in the operating systems, it is even possible to connect a PCIe storage enclosure to two different systems for maximum high availability.