Follow these cabling best practices when deploying a full mesh switchless interconnect. The Dell factory populates PCIe network adapters consistently, but the slot enumeration sequence depends on platform and riser configuration. PCIe slot identification is labeled on the chassis, and Port 1 and Port 2 are physically labeled on the PCIe NIC adapter bracket.
Note: PCIe riser orientation may change the port orientation on each network adapter. Therefore, some network adapters may have a physically reversed orientation depending on which PCIe slot the network adapter is installed. Be certain to check the orientation of Port 1 and Port 2 on each network adapter, as shown in the following figure.
Figure 3. Port orientation
Use the following procedure when cabling the switchless cluster nodes for single-link or dual-link full mesh storage interconnect:
Starting with Node 1, cable the PCIe network adapter in the lowest slot number (Port 1) to the same adapter slot (Port 1) on Node 2.
Continue cabling a single-link on Node 1 to every other cluster node. Cable the adapter ports on Node 1 in ascending order (for example, Slot 3 Port 1, Slot 3 Port 2, Slot 4 Port 1) to the adapter in the lowest slot that is in the lowest port of each incremental cluster node or nodes.
For Node 2, cable the next available adapter port to the next available adapter port on Node 3. Then incrementally cable an additional port on Node 2 to the next available port on Node 4 (where applicable).
For Node 3, cable the next available adapter port to the next available adapter port on Node 4.
For a dual-link full mesh interconnect, repeat steps 2 to 4 beginning with the next available adapter port on each cluster node.
Apply labels to each end of each cable with rack unit (RackU), slot, and port identification to ensure that the cables are correctly connected in case a server chassis needs to be uncabled.
The figures in the next sections illustrate the AX-740xd platform to display the networks required for storage network traffic. Different platforms and riser configurations use different PCIe slots and orientations. However, the cabling guidance remains consistent with the best practices that are listed above.
Three-node, single-link full mesh switchless interconnect
The following figure shows an example of a three-node cluster that is configured with a single-link full mesh storage network interconnect. External network traffic uses the LOM/rNDC/OCP integrated network adapter, while storage network traffic uses one RDMA-capable PCIe network adapter for each server node. The management network offers some redundancy in the event of a storage network connectivity (cable or port) failure.
This figure shows the three storage networks that are needed to create a single-link full mesh interconnect between three clustered nodes. The numbered blue lines indicate the recommended cabling order, beginning with the RDMA-capable PCIe network adapter in the lowest slot number, Port 1.
Note: In the following examples, the RDMA-capable network adapter is installed on Slot #6. Depending on the chassis configuration, the ports may be reversed.
After cabling storage, connect all nodes, LOM/rNDC/OCP, and Ports 1 and 2 to a management/VM network.
Figure 4. Three-node, single-link full mesh cabling
Table 4. Port link connections
Node
First port link connection
Second port link connection
Node 1
Storage1-2
Storage1-3
Node 2
Storage1-2
Storage2-3
Node 3
Storage1-3
Storage2-3
Four-node, single-link full mesh switchless interconnect
The following figure shows the six storage networks needed to create a single-link full mesh interconnect between four clustered nodes. The numbered blue lines indicate the recommended cabling order, beginning with the RDMA-capable PCIe network adapter in the lowest slot number (Port 1). After cabling storage, connect all nodes, LOM/rNDC/OCP, and Ports 1 and 2 to a management/VM network.
Figure 5. Four-node, single-link full mesh cabling
Table 5. Port link connections
Node
First port link connection
Second port link connection
Third port link connection
Node 1
Storage1-2
Storage1-3
Storage1-4
Node 2
Storage1-2
Storage2-3
Storage2-4
Node 3
Storage1-3
Storage2-3
Storage3-4
Node 4
Storage1-4
Storage2-4
Storage3-4
Two-node, back-to-back connected architecture
The following figure shows the two storage networks needed to create a dual-link direct interconnect between two clustered nodes (also known as back-to-back). The numbered blue lines indicate the recommended cabling order, beginning with the network adapter in the lowest slot number (port 1). After cabling storage, connect all nodes, LOM/rNDC/OCP, and ports 1 and 2 to a management/VM network.
Note: The two-node, back-to-back storage topology supports all available RDMA-based network adapters that are supported in the solution.
Figure 6. Two-node dual-link direct cabling
Three-node, dual-link full mesh switchless interconnect
The following figure shows an example of a three-node cluster that is configured with a dual-link full mesh storage network interconnect. External network traffic uses the LOM/rNDC/OCP integrated network adapter, while storage network traffic uses two RDMA-capable PCIe adapters for each server node. In this case, each clustered node has redundant storage network connectivity to every other node in the cluster.
The following figure shows the six storage networks needed to create a dual-link full mesh interconnect between three clustered nodes. The numbered blue lines indicate the recommended cabling order, beginning with the RDMA adapter in the lowest slot number (Port 1). After cabling storage, connect all nodes, LOM/rNDC/OCP, and Ports 1 and 2 to a management/VM network.
Figure 7. Three-node, dual-link full mesh cabling
Table 6. Port link connections
Node
First port link connection
Second port link connection
Third port link connection
Fourth port link connection
Node 1
Storage1-2
Storage1-3
Storage2-1
Storage3-1
Node 2
Storage1-2
Storage2-3
Storage2-1
Storage3-2
Node 3
Storage1-3
Storage2-3
Storage3-1
Storage3-2
Four-node, dual-link full mesh switchless interconnect
The following figure shows the twelve storage networks needed to create a dual-link full mesh interconnect between four clustered nodes. The numbered blue lines indicate the recommended cabling order, beginning with the RDMA-capable PCIe adapter in the lowest slot number, Port 1. After cabling storage, connect all nodes, LOM/rNDC/OCP, and Ports 1 and 2 to a management/VM network.