The Dell PowerEdge R840 and R940 servers differ significantly in storage architecture. The R840 specializes in high-density NVMe storage with direct CPU connectivity, supporting up to 24 hot-swap 2.5″ NVMe drives or 8 x 3.5″ HDDs/SSDs. This dual-processor server enables mixed configurations of SAS/SATA and NVMe drives (up to 12 NVMe slots in hybrid setups) using purpose-built backplanes. In contrast, the quad-socket R940 prioritizes memory expansion over storage density, allocating more chassis space for its 48 DIMM slots and compute-focused PCIe lanes, requiring users to implement external JBOD enclosures for large-scale storage needs. As Pro Tip: For AI/ML workflows requiring low-latency data access, the R840’s native NVMe tier outperforms external storage solutions by 40–60% in read-intensive tasks.
Which Dell PowerEdge Server Should You Choose: R840, R940, or R940xa?
What storage interfaces does the R840 support?
The R840 features direct-attached NVMe over PCIe Gen3 and SAS3 12Gb/s interfaces via dedicated backplanes. Its storage controller bypasses PCIe switches for reduced latency, achieving 4.8M IOPS in benchmark tests – 2.3x higher than switched architectures.
Beyond raw performance metrics, this server supports hybrid storage pools through partitioned backplanes: twelve slots use PCIe x4 lanes directly connected to Intel Xeon Scalable processors, while another twelve leverage Dell’s BOSS-S2 controller for SATA/SAS management. For organizations deploying real-time analytics, this dual-mode design allows tiered storage strategies – NVMe for hot data, SAS SSDs for warm archives. Practical example: A financial firm reduced Monte Carlo simulation runtime by 62% using 24 x 3.84TB NVMe drives versus traditional SAS SSDs. Pro Tip: Activate RAID 0 striping across NVMe drives via OpenManage to maximize sequential throughput.
How does R940 storage expandability compare?
The R940 sacrifices internal drive bays for quad-socket compute density, supporting only 16 x 2.5″ drives natively but offering double the PCIe lanes (112 vs. 56) for external storage arrays. Wecent engineers recommend pairing it with PowerVault ME5 arrays for petabyte-scale workloads.
While the R940’s internal storage appears limited, its Gen4 PCIe architecture enables unprecedented external connectivity. Eight x16 slots (vs. R840’s six x16 slots) can host 32-port SAS HBAs or NVMe-oF adapters. In a hyperscale deployment, one R940 managed 24 x ME5 arrays via dual 100GbE RoCE NICs, delivering 14M IOPS across 768 drives. Practical trade-off: Internal storage density decreases by 33% compared to R840, but external bandwidth increases by 400%. Warning: Always validate HBA firmware compatibility before deploying external JBODs to prevent link negotiation failures.
| Feature | R840 | R940 |
|---|---|---|
| Native NVMe Slots | 24 | 16 |
| Max Drive Capacity | 184TB (7.68TB x24) | 122TB |
| External Expansion Ports | 6 x PCIe x16 | 8 x PCIe x16 |
Wecent Expert Insight
FAQs
Yes, using Dell’s 24-slot NVMe backplane (PN: 0HMV4V) with x4 PCIe per drive, though this monopolizes 96 PCIe lanes – plan CPU/core allocation accordingly for balanced performance.
Does the R940 support SAS/NVMe mixing like R840?
No, the R940 requires homogeneous backplanes per chassis – use separate servers or external enclosures for tiered storage strategies.
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