The SAP HANA nodes connect to the Unity arrays through a Fibre Channel SAN. SAN components require a minimum 8 Gb/s link speed, and the SAN topology must follow best practices for all redundant components and links.
The connectivity, which includes host HBAs, SAN ports, switches, and array front-end ports, requires careful planning. Unity provides multiple options for front-end connectivity through on-board ports directly on the DPE and optional I/O modules whose configuration must match between SPs. Fibre Channel I/O module ports use 16 Gb SFPs. 16 Gb FC is recommended for the best performance. All Fibre Channel ports can negotiate to lower speeds.
The SAP HANA KPIs for TDI deployments require a maximum bandwidth of 400 MB/s per SAP HANA node. If, for example, ten nodes are connected in a SAN to a Unity array, a total bandwidth of 4000 MB/s is required. Assuming a 16 Gb/s front-end port provides approximately 1500 MBps bandwidth, four dedicated 16 Gb/s front-end ports are recommended to support ten SAP HANA nodes (4 x 1500 MB/s = 6000 MB/s), two on each SP, to facilitate high availability, load-balancing, and continued connectivity in the event of SP failure.
While this maximum bandwidth requirement is only seen in the unlikely event that all nodes have this requirement simultaneously, it is one of the SAP HANA certification criteria that the storage arrays must sustain this peak workload.
This requirement does not just affect the storage front-end configuration. In the example with ten nodes, the complete path through the SAN network must be configured to support the maximum bandwidth also.
Each HBA port (initiator) creates a path for I/Os between the host and the SAN switch, which then continues to the Unity storage. If a host only uses a single HBA port, it will have a single I/O path that serves all I/Os. Such a design is not advisable, because a single path does not provide HA and also risks a potential bottleneck during high I/O activity due to the lack of additional ports for load-balancing.
A better design provides each SAP HANA server with at least two HBA ports, preferably on two separate HBAs. The additional ports provide more connectivity and also allow the Linux DM-MPIO to load-balance and failover across HBA paths.
Unity is a unified array providing block and file connectivity. Even though file storage can be used in an SAP HANA environment for different purposes (such as PXE-boot and shared file systems), the SAP TDI certification of the Unity series array applies to block Fibre Channel (FC)-attached SAP HANA persistence (data and log) only.
Special attention is required when you connect SAP HANA nodes to the front-end FC ports of a Unity array. The Unity series provides flexible connectivity options through Dell EMC UltraFlexTM I/O modules for both the file for NFS/SMB connectivity and the block storage for FC and iSCSI host connectivity.
The block connectivity for the SAP HANA persistence requires the UltraFlex I/O FC module (block only) on each storage processor with 4 x 16 GB/s FC ports. Each Unity model supports up to two UltraFlex I/O modules per SP.
Each SAP HANA node must connect to a minimum of two FC ports on each storage processor. Figure 5 shows the recommended FC port connectivity on an UltraFlex I/O module on each storage processor.
Figure 5. Rear view of Unity DPE
To achieve full I/O performance for SAP HANA production deployments, implement the following FC port requirements for a Unity array: