Short answer: on VMware Cloud Foundation 9 with NFS storage, the network decision that matters most for SAP HANA is whether vMotion and the NFS log write flow share the same vNICs and RX queues. With 2 or 4 vNICs (the VCF 9 simple and workload-separation models), a vMotion of a large HANA VM fills the same queues that carry the HANA log writes, and commit latency rises. The VCF 9.1 storage-and-workload-separation model (6 NICs) and the FlexPod TDI layout (7 vNICs) give storage its own vNICs, queues, MTU and QoS class. The simulator below shows the mechanism on Cisco UCS VIC 1380, VIC 15231 and HPE Synergy 6310C.
Four network layouts compared
| Layout | vNICs | RX queues per vNIC | Interrupts | vMotion vs log I/O | Log I/O vs VM traffic | QoS / MTU per traffic class | Matches |
|---|---|---|---|---|---|---|---|
| 2 vNIC (VCF 9 simple model) | 2 | 16 | 40 | Shared queues | Shared | NIOC only | VCF 9 design library |
| 4 vNIC (VCF 9 workload separation) | 4 | 16 / 8 | 64 | Shared queues | Isolated | NIOC only | VCF 9 design library |
| 6 vNIC (VCF 9 storage and workload separation) | 6 | 8 | 72 | Isolated | Isolated | Yes | VCF 9 design library |
| 7 vNIC (TDI, FlexPod CVD) | 7 | 8 | 84 | Isolated | Isolated | Yes | FlexPod CVD for SAP HANA TDI |
Two facts shape the comparison. VCF 9 allows a single vmk_vmotion per host (SDDC Manager reports “Host is not conforming with the requirement of single vmknic for vMotion/management traffic type”, KB 407383), so one vMotion is capped by one uplink, and Multi-NIC vMotion is a vSphere or VVF option only. Separating vNICs doesn’t add bandwidth on the shared uplink to the IOM. It separates queue servicing, CPU cores, MTU and QoS, which is what protects the log write latency.
How to use the simulator
- Pick the adapter (VIC 1380 2×40G, VIC 15231 2×100G, Synergy 6310C 2×50G) and one of the four layouts.
- Start a vMotion of a 2 TB HANA VM, alone or 2, 4 or 8 in parallel, and watch the NFS log write latency against the 1 ms orientation KPI used by HCMT, the RX_NO_BUFS drops and the uplink load per fabric.
- Toggle NFS
nconnect, UCS QoS (storage platinum, vMotion bronze) and Multi-NIC vMotion to see what each one changes.
It is an illustrative model, not a measurement: one RX queue is served by one core at about 4 Gb/s, vMotion uses 4 streams per VM with one vmk_vmotion, and the NFS log flow is 1 Gb/s. Validate any design with HCMT on your own hardware.
SAP HANA on VCF 9: the design areas
| Area | Read |
|---|---|
| Network and vNIC layout | VCF 9 SAP HANA network design: why 6 NICs matter for vMotion and NFS |
| vMotion of large HANA VMs | Multi-NIC vMotion tuning: 2×40 Gbps for SAP HANA VMs |
| NFS storage | ESXi NFS nConnect and nConnect for NFS 4.1 datastores |
| Cisco UCS adapter policy | VMware-v2 adapter policy for Cisco VIC |
| Storage I/O control | SIOC deprecation in vSphere 8.0 U3 and removal in vSphere 9 |
| Hardware support | How to check VCF 9 hardware compatibility |
| Edition | vSphere editions comparison: Standard vs VVF vs VCF |
Sources
- Broadcom TechDocs, VCF 9.1 design library: simple network model, workload separation, storage and workload separation
- Cisco: FlexPod Datacenter with Cisco UCS X-Series for SAP HANA TDI
- SAP: SAP HANA on VMware vSphere (SAP support content)
- Broadcom KB 407383: Host is not conforming with the requirement of single vmknic for vMotion/management traffic type
- HPE: HPE Synergy reference document